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	$100.89	10.513%	$111.4966	$111.50	$111.50	$111.50
Purchase #2	$124.31	12.173%	$139.4423	$139.44	$139.45	$139.40
Purchase #3	$52.57	13.805%	$59.8273	$59.83	$59.85	$59.80
Purchase #4	$177.47	9.429%	$194.2036	$194.20	$194.20	$194.20
Purchase #5	$137.29	7.342%	$147.3698	$147.37	$147.35	$147.40
Purchase #6	$108.72	5.457%	$114.6529	$114.65	$114.65	$114.70
Purchase #7	$107.28	9.219%	$117.1701	$117.17	$117.15	$117.20
7 purchase totals =	$808.53		$884.1626	$884.16	$884.15	$884.20