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	$174.42	6.313%	$185.4311	$185.43	$185.45	$185.40
Purchase #2	$151.86	13.320%	$172.0878	$172.09	$172.10	$172.10
Purchase #3	$196.46	10.557%	$217.2003	$217.20	$217.20	$217.20
Purchase #4	$28.62	12.827%	$32.2911	$32.29	$32.30	$32.30
Purchase #5	$235.77	6.397%	$250.8522	$250.85	$250.85	$250.90
Purchase #6	$41.49	3.483%	$42.9351	$42.94	$42.95	$42.90
Purchase #7	$50.39	9.289%	$55.0707	$55.07	$55.05	$55.10
7 purchase totals =	$879.01		$955.8683	$955.87	$955.90	$955.90