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	$88.59	5.757%	$93.6901	$93.69	$93.70	$93.70
Purchase #2	$235.73	5.833%	$249.4801	$249.48	$249.50	$249.50
Purchase #3	$247.97	4.673%	$259.5576	$259.56	$259.55	$259.60
Purchase #4	$40.69	12.865%	$45.9248	$45.92	$45.90	$45.90
Purchase #5	$105.77	5.665%	$111.7619	$111.76	$111.75	$111.80
Purchase #6	$203.84	10.845%	$225.9464	$225.95	$225.95	$225.90
Purchase #7	$160.51	13.493%	$182.1676	$182.17	$182.15	$182.20
7 purchase totals =	$1,083.10		$1,168.5285	$1,168.53	$1,168.50	$1,168.60