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	$201.94	10.198%	$222.5338	$222.53	$222.55	$222.50
Purchase #2	$193.61	7.806%	$208.7232	$208.72	$208.70	$208.70
Purchase #3	$55.60	10.264%	$61.3068	$61.31	$61.30	$61.30
Purchase #4	$227.64	10.352%	$251.2053	$251.21	$251.20	$251.20
Purchase #5	$10.63	12.461%	$11.9546	$11.95	$11.95	$12.00
Purchase #6	$180.86	8.575%	$196.3687	$196.37	$196.35	$196.40
Purchase #7	$221.83	9.323%	$242.5112	$242.51	$242.50	$242.50
7 purchase totals =	$1,092.11		$1,194.6036	$1,194.60	$1,194.55	$1,194.60