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	$101.53	9.605%	$111.282	$111.28	$111.30	$111.30
Purchase #2	$83.40	3.758%	$86.5342	$86.53	$86.55	$86.50
Purchase #3	$43.91	12.315%	$49.3175	$49.32	$49.30	$49.30
Purchase #4	$237.67	13.560%	$269.8981	$269.90	$269.90	$269.90
Purchase #5	$172.55	7.841%	$186.0796	$186.08	$186.10	$186.10
Purchase #6	$45.97	9.139%	$50.1712	$50.17	$50.15	$50.20
Purchase #7	$200.60	12.496%	$225.667	$225.67	$225.65	$225.70
7 purchase totals =	$885.63		$978.9496	$978.95	$978.95	$979.00