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	$197.54	12.267%	$221.7722	$221.77	$221.75	$221.80
Purchase #2	$233.92	13.215%	$264.8325	$264.83	$264.85	$264.80
Purchase #3	$30.69	5.449%	$32.3623	$32.36	$32.35	$32.40
Purchase #4	$213.28	5.148%	$224.2597	$224.26	$224.25	$224.30
Purchase #5	$64.42	9.443%	$70.5032	$70.50	$70.50	$70.50
Purchase #6	$52.78	8.611%	$57.3249	$57.32	$57.30	$57.30
Purchase #7	$151.44	9.155%	$165.3043	$165.30	$165.30	$165.30
7 purchase totals =	$944.07		$1,036.3591	$1,036.34	$1,036.30	$1,036.40