Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$111.45	13.236%	$126.2015	$126.20	$126.20	$126.20
Purchase #2	$184.47	6.516%	$196.4901	$196.49	$196.50	$196.50
Purchase #3	$162.69	4.242%	$169.5913	$169.59	$169.60	$169.60
Purchase #4	$203.48	9.429%	$222.6661	$222.67	$222.65	$222.70
Purchase #5	$134.58	5.627%	$142.1528	$142.15	$142.15	$142.20
Purchase #6	$227.89	11.635%	$254.405	$254.41	$254.40	$254.40
Purchase #7	$240.97	5.492%	$254.2041	$254.20	$254.20	$254.20
7 purchase totals =	$1,265.53		$1,365.7109	$1,365.71	$1,365.70	$1,365.80