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	$185.40	4.869%	$194.4271	$194.43	$194.45	$194.40
Purchase #2	$152.76	12.178%	$171.3631	$171.36	$171.35	$171.40
Purchase #3	$150.97	12.254%	$169.4699	$169.47	$169.45	$169.50
Purchase #4	$180.51	11.179%	$200.6892	$200.69	$200.70	$200.70
Purchase #5	$87.30	3.139%	$90.0403	$90.04	$90.05	$90.00
Purchase #6	$246.67	6.366%	$262.373	$262.37	$262.35	$262.40
Purchase #7	$157.34	10.520%	$173.8922	$173.89	$173.90	$173.90
7 purchase totals =	$1,160.95		$1,262.2548	$1,262.25	$1,262.25	$1,262.30