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	$118.98	7.516%	$127.9225	$127.92	$127.90	$127.90
Purchase #2	$99.61	11.105%	$110.6717	$110.67	$110.65	$110.70
Purchase #3	$123.51	11.207%	$137.3518	$137.35	$137.35	$137.40
Purchase #4	$55.30	11.750%	$61.7978	$61.80	$61.80	$61.80
Purchase #5	$53.81	9.118%	$58.7164	$58.72	$58.70	$58.70
Purchase #6	$25.78	7.601%	$27.7395	$27.74	$27.75	$27.70
Purchase #7	$94.35	5.578%	$99.6128	$99.61	$99.60	$99.60
7 purchase totals =	$571.34		$623.8125	$623.81	$623.75	$623.80