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	$138.82	8.681%	$150.871	$150.87	$150.85	$150.90
Purchase #2	$71.66	13.336%	$81.2166	$81.22	$81.20	$81.20
Purchase #3	$221.91	9.145%	$242.2037	$242.20	$242.20	$242.20
Purchase #4	$244.83	5.432%	$258.1292	$258.13	$258.15	$258.10
Purchase #5	$33.28	12.754%	$37.5245	$37.52	$37.50	$37.50
Purchase #6	$141.97	5.755%	$150.1404	$150.14	$150.15	$150.10
Purchase #7	$105.25	12.520%	$118.4273	$118.43	$118.45	$118.40
7 purchase totals =	$957.72		$1,038.5127	$1,038.51	$1,038.50	$1,038.40