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	$226.51	10.266%	$249.7635	$249.76	$249.75	$249.80
Purchase #2	$105.78	5.289%	$111.3747	$111.37	$111.35	$111.40
Purchase #3	$127.76	9.479%	$139.8704	$139.87	$139.85	$139.90
Purchase #4	$234.89	4.804%	$246.1741	$246.17	$246.15	$246.20
Purchase #5	$55.32	11.643%	$61.7609	$61.76	$61.75	$61.80
Purchase #6	$203.52	3.213%	$210.0591	$210.06	$210.05	$210.10
Purchase #7	$32.65	4.256%	$34.0396	$34.04	$34.05	$34.00
7 purchase totals =	$986.43		$1,053.0423	$1,053.03	$1,052.95	$1,053.20