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	$139.97	8.660%	$152.0914	$152.09	$152.10	$152.10
Purchase #2	$166.53	11.645%	$185.9224	$185.92	$185.90	$185.90
Purchase #3	$57.30	3.758%	$59.4533	$59.45	$59.45	$59.50
Purchase #4	$221.40	7.636%	$238.3061	$238.31	$238.30	$238.30
Purchase #5	$237.70	6.733%	$253.7043	$253.70	$253.70	$253.70
Purchase #6	$26.88	6.251%	$28.5603	$28.56	$28.55	$28.60
Purchase #7	$100.25	11.119%	$111.3968	$111.40	$111.40	$111.40
7 purchase totals =	$950.03		$1,029.4346	$1,029.43	$1,029.40	$1,029.50