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	$89.66	13.380%	$101.6565	$101.66	$101.65	$101.70
Purchase #2	$48.73	11.715%	$54.4387	$54.44	$54.45	$54.40
Purchase #3	$73.77	3.616%	$76.4375	$76.44	$76.45	$76.40
Purchase #4	$211.57	5.321%	$222.8276	$222.83	$222.85	$222.80
Purchase #5	$154.60	11.300%	$172.0698	$172.07	$172.05	$172.10
Purchase #6	$28.67	5.758%	$30.3208	$30.32	$30.30	$30.30
Purchase #7	$221.57	8.860%	$241.2011	$241.20	$241.20	$241.20
7 purchase totals =	$828.57		$898.9520	$898.96	$898.95	$898.90