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	$177.64	7.242%	$190.5047	$190.50	$190.50	$190.50
Purchase #2	$75.91	12.188%	$85.1619	$85.16	$85.15	$85.20
Purchase #3	$122.26	7.846%	$131.8525	$131.85	$131.85	$131.90
Purchase #4	$137.88	13.312%	$156.2346	$156.23	$156.25	$156.20
Purchase #5	$174.83	11.393%	$194.7484	$194.75	$194.75	$194.70
Purchase #6	$132.56	4.530%	$138.565	$138.57	$138.55	$138.60
Purchase #7	$48.42	3.869%	$50.2934	$50.29	$50.30	$50.30
7 purchase totals =	$869.50		$947.3605	$947.35	$947.35	$947.40