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	$88.28	7.505%	$94.9054	$94.91	$94.90	$94.90
Purchase #2	$168.93	5.553%	$178.3107	$178.31	$178.30	$178.30
Purchase #3	$46.95	4.505%	$49.0651	$49.07	$49.05	$49.10
Purchase #4	$42.96	8.496%	$46.6099	$46.61	$46.60	$46.60
Purchase #5	$32.65	9.677%	$35.8095	$35.81	$35.80	$35.80
Purchase #6	$42.48	13.323%	$48.1396	$48.14	$48.15	$48.10
Purchase #7	$59.82	12.381%	$67.2263	$67.23	$67.25	$67.20
7 purchase totals =	$482.07		$520.0665	$520.08	$520.05	$520.00