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	$111.64	12.639%	$125.7502	$125.75	$125.75	$125.80
Purchase #2	$208.98	10.290%	$230.484	$230.48	$230.50	$230.50
Purchase #3	$65.97	8.204%	$71.3822	$71.38	$71.40	$71.40
Purchase #4	$22.72	11.109%	$25.244	$25.24	$25.25	$25.20
Purchase #5	$153.51	12.314%	$172.4132	$172.41	$172.40	$172.40
Purchase #6	$53.72	4.674%	$56.2309	$56.23	$56.25	$56.20
Purchase #7	$38.46	13.873%	$43.7956	$43.80	$43.80	$43.80
7 purchase totals =	$655.00		$725.3001	$725.29	$725.35	$725.30