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	$235.68	7.514%	$253.389	$253.39	$253.40	$253.40
Purchase #2	$91.38	9.130%	$99.723	$99.72	$99.70	$99.70
Purchase #3	$209.59	3.300%	$216.5065	$216.51	$216.50	$216.50
Purchase #4	$184.99	13.401%	$209.7805	$209.78	$209.80	$209.80
Purchase #5	$132.72	11.444%	$147.9085	$147.91	$147.90	$147.90
Purchase #6	$183.85	7.805%	$198.1995	$198.20	$198.20	$198.20
Purchase #7	$176.34	11.258%	$196.1924	$196.19	$196.20	$196.20
7 purchase totals =	$1,214.55		$1,321.6994	$1,321.70	$1,321.70	$1,321.70