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	$207.40	13.300%	$234.9842	$234.98	$235.00	$235.00
Purchase #2	$96.35	4.635%	$100.8158	$100.82	$100.80	$100.80
Purchase #3	$6.99	11.780%	$7.8134	$7.81	$7.80	$7.80
Purchase #4	$34.45	9.811%	$37.8299	$37.83	$37.85	$37.80
Purchase #5	$98.67	12.575%	$111.0778	$111.08	$111.10	$111.10
Purchase #6	$225.73	6.625%	$240.6846	$240.68	$240.70	$240.70
Purchase #7	$195.29	8.795%	$212.4658	$212.47	$212.45	$212.50
7 purchase totals =	$864.88		$945.6715	$945.67	$945.70	$945.70