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	$130.92	13.687%	$148.839	$148.84	$148.85	$148.80
Purchase #2	$221.41	13.172%	$250.5741	$250.57	$250.55	$250.60
Purchase #3	$84.29	5.519%	$88.942	$88.94	$88.95	$88.90
Purchase #4	$30.65	9.438%	$33.5427	$33.54	$33.55	$33.50
Purchase #5	$37.39	13.761%	$42.5352	$42.54	$42.55	$42.50
Purchase #6	$132.89	11.756%	$148.5125	$148.51	$148.50	$148.50
Purchase #7	$35.28	12.367%	$39.6431	$39.64	$39.65	$39.60
7 purchase totals =	$672.83		$752.5886	$752.58	$752.60	$752.40