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	$199.88	12.574%	$225.0129	$225.01	$225.00	$225.00
Purchase #2	$235.57	11.755%	$263.2613	$263.26	$263.25	$263.30
Purchase #3	$48.55	12.466%	$54.6022	$54.60	$54.60	$54.60
Purchase #4	$176.51	12.103%	$197.873	$197.87	$197.85	$197.90
Purchase #5	$155.67	4.375%	$162.4806	$162.48	$162.50	$162.50
Purchase #6	$95.85	10.497%	$105.9114	$105.91	$105.90	$105.90
Purchase #7	$79.34	11.198%	$88.2245	$88.22	$88.20	$88.20
7 purchase totals =	$991.37		$1,097.3659	$1,097.35	$1,097.30	$1,097.40