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	$17.36	4.664%	$18.1697	$18.17	$18.15	$18.20
Purchase #2	$74.59	4.802%	$78.1718	$78.17	$78.15	$78.20
Purchase #3	$138.70	9.192%	$151.4493	$151.45	$151.45	$151.40
Purchase #4	$108.95	12.849%	$122.949	$122.95	$122.95	$122.90
Purchase #5	$71.47	9.708%	$78.4083	$78.41	$78.40	$78.40
Purchase #6	$129.30	5.215%	$136.043	$136.04	$136.05	$136.00
Purchase #7	$151.56	7.226%	$162.5117	$162.51	$162.50	$162.50
7 purchase totals =	$691.93		$747.7028	$747.70	$747.65	$747.60