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	$89.75	3.381%	$92.7844	$92.78	$92.80	$92.80
Purchase #2	$89.29	5.550%	$94.2456	$94.25	$94.25	$94.20
Purchase #3	$55.64	3.115%	$57.3732	$57.37	$57.35	$57.40
Purchase #4	$50.86	4.456%	$53.1263	$53.13	$53.15	$53.10
Purchase #5	$218.55	11.719%	$244.1619	$244.16	$244.15	$244.20
Purchase #6	$120.95	5.646%	$127.7788	$127.78	$127.80	$127.80
Purchase #7	$184.42	11.500%	$205.6283	$205.63	$205.65	$205.60
7 purchase totals =	$809.46		$875.0985	$875.10	$875.15	$875.10