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	$33.59	11.124%	$37.3266	$37.33	$37.35	$37.30
Purchase #2	$235.48	8.571%	$255.663	$255.66	$255.65	$255.70
Purchase #3	$176.91	11.843%	$197.8615	$197.86	$197.85	$197.90
Purchase #4	$67.28	8.714%	$73.1428	$73.14	$73.15	$73.10
Purchase #5	$214.25	11.222%	$238.2931	$238.29	$238.30	$238.30
Purchase #6	$225.28	3.619%	$233.4329	$233.43	$233.45	$233.40
Purchase #7	$101.90	8.408%	$110.4678	$110.47	$110.45	$110.50
7 purchase totals =	$1,054.69		$1,146.1877	$1,146.18	$1,146.20	$1,146.20