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	$56.77	4.685%	$59.4297	$59.43	$59.45	$59.40
Purchase #2	$157.62	9.287%	$172.2582	$172.26	$172.25	$172.30
Purchase #3	$226.92	10.690%	$251.1777	$251.18	$251.20	$251.20
Purchase #4	$116.73	11.680%	$130.3641	$130.36	$130.35	$130.40
Purchase #5	$214.86	6.274%	$228.3403	$228.34	$228.35	$228.30
Purchase #6	$52.57	9.503%	$57.5657	$57.57	$57.55	$57.60
Purchase #7	$209.87	8.828%	$228.3973	$228.40	$228.40	$228.40
7 purchase totals =	$1,035.34		$1,127.5330	$1,127.54	$1,127.55	$1,127.60