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	$56.45	8.861%	$61.452	$61.45	$61.45	$61.50
Purchase #2	$36.89	10.317%	$40.6959	$40.70	$40.70	$40.70
Purchase #3	$161.37	5.639%	$170.4697	$170.47	$170.45	$170.50
Purchase #4	$98.94	13.462%	$112.2593	$112.26	$112.25	$112.30
Purchase #5	$37.32	8.789%	$40.6001	$40.60	$40.60	$40.60
Purchase #6	$96.74	5.782%	$102.3335	$102.33	$102.35	$102.30
Purchase #7	$71.92	5.369%	$75.7814	$75.78	$75.80	$75.80
7 purchase totals =	$559.63		$603.5919	$603.59	$603.60	$603.70