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	$226.98	11.735%	$253.6161	$253.62	$253.60	$253.60
Purchase #2	$32.67	13.348%	$37.0308	$37.03	$37.05	$37.00
Purchase #3	$74.32	4.408%	$77.596	$77.60	$77.60	$77.60
Purchase #4	$65.94	8.549%	$71.5772	$71.58	$71.60	$71.60
Purchase #5	$152.39	13.277%	$172.6228	$172.62	$172.60	$172.60
Purchase #6	$23.56	7.864%	$25.4128	$25.41	$25.40	$25.40
Purchase #7	$40.96	8.428%	$44.4121	$44.41	$44.40	$44.40
7 purchase totals =	$616.82		$682.2678	$682.27	$682.25	$682.20