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	$116.95	8.715%	$127.1422	$127.14	$127.15	$127.10
Purchase #2	$170.93	8.657%	$185.7274	$185.73	$185.75	$185.70
Purchase #3	$210.35	10.865%	$233.2045	$233.20	$233.20	$233.20
Purchase #4	$21.55	6.451%	$22.9402	$22.94	$22.95	$22.90
Purchase #5	$65.48	3.176%	$67.5596	$67.56	$67.55	$67.60
Purchase #6	$140.84	9.681%	$154.4747	$154.47	$154.45	$154.50
Purchase #7	$143.65	10.346%	$158.512	$158.51	$158.50	$158.50
7 purchase totals =	$869.75		$949.5606	$949.55	$949.55	$949.50