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	$40.87	13.513%	$46.3928	$46.39	$46.40	$46.40
Purchase #2	$18.71	9.532%	$20.4934	$20.49	$20.50	$20.50
Purchase #3	$174.67	5.827%	$184.848	$184.85	$184.85	$184.80
Purchase #4	$51.55	7.809%	$55.5755	$55.58	$55.60	$55.60
Purchase #5	$20.29	9.443%	$22.206	$22.21	$22.20	$22.20
Purchase #6	$197.51	10.341%	$217.9345	$217.93	$217.95	$217.90
Purchase #7	$67.57	6.717%	$72.1087	$72.11	$72.10	$72.10
7 purchase totals =	$571.17		$619.5589	$619.56	$619.60	$619.50