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	$88.65	4.830%	$92.9318	$92.93	$92.95	$92.90
Purchase #2	$25.78	6.393%	$27.4281	$27.43	$27.45	$27.40
Purchase #3	$48.36	3.760%	$50.1783	$50.18	$50.20	$50.20
Purchase #4	$227.50	4.369%	$237.4395	$237.44	$237.45	$237.40
Purchase #5	$120.72	8.286%	$130.7229	$130.72	$130.70	$130.70
Purchase #6	$101.71	9.732%	$111.6084	$111.61	$111.60	$111.60
Purchase #7	$42.87	7.120%	$45.9223	$45.92	$45.90	$45.90
7 purchase totals =	$655.59		$696.2313	$696.23	$696.25	$696.10