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	$198.35	7.108%	$212.4487	$212.45	$212.45	$212.40
Purchase #2	$200.33	11.259%	$222.8852	$222.89	$222.90	$222.90
Purchase #3	$168.74	6.123%	$179.072	$179.07	$179.05	$179.10
Purchase #4	$217.90	11.211%	$242.3288	$242.33	$242.35	$242.30
Purchase #5	$228.62	9.528%	$250.4029	$250.40	$250.40	$250.40
Purchase #6	$204.85	5.763%	$216.6555	$216.66	$216.65	$216.70
Purchase #7	$29.60	9.850%	$32.5156	$32.52	$32.50	$32.50
7 purchase totals =	$1,248.39		$1,356.3087	$1,356.32	$1,356.30	$1,356.30