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	$165.29	10.527%	$182.6901	$182.69	$182.70	$182.70
Purchase #2	$216.44	7.769%	$233.2552	$233.26	$233.25	$233.30
Purchase #3	$36.50	9.140%	$39.8361	$39.84	$39.85	$39.80
Purchase #4	$57.36	3.748%	$59.5099	$59.51	$59.50	$59.50
Purchase #5	$156.72	10.290%	$172.8465	$172.85	$172.85	$172.80
Purchase #6	$124.38	11.369%	$138.5208	$138.52	$138.50	$138.50
Purchase #7	$98.65	12.661%	$111.1401	$111.14	$111.15	$111.10
7 purchase totals =	$855.34		$937.7987	$937.81	$937.80	$937.70