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	$234.63	5.114%	$246.629	$246.63	$246.65	$246.60
Purchase #2	$185.64	12.738%	$209.2868	$209.29	$209.30	$209.30
Purchase #3	$16.94	9.563%	$18.56	$18.56	$18.55	$18.60
Purchase #4	$201.93	12.612%	$227.3974	$227.40	$227.40	$227.40
Purchase #5	$222.51	5.763%	$235.3333	$235.33	$235.35	$235.30
Purchase #6	$72.47	8.594%	$78.6981	$78.70	$78.70	$78.70
Purchase #7	$40.54	13.210%	$45.8953	$45.90	$45.90	$45.90
7 purchase totals =	$974.66		$1,061.7999	$1,061.81	$1,061.85	$1,061.80