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	$55.47	6.715%	$59.1948	$59.19	$59.20	$59.20
Purchase #2	$232.60	6.315%	$247.2887	$247.29	$247.30	$247.30
Purchase #3	$198.74	11.434%	$221.4639	$221.46	$221.45	$221.50
Purchase #4	$75.33	3.625%	$78.0607	$78.06	$78.05	$78.10
Purchase #5	$39.30	6.150%	$41.717	$41.72	$41.70	$41.70
Purchase #6	$108.60	9.702%	$119.1364	$119.14	$119.15	$119.10
Purchase #7	$117.42	8.373%	$127.2516	$127.25	$127.25	$127.30
7 purchase totals =	$827.46		$894.1131	$894.11	$894.10	$894.20