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	$225.26	9.851%	$247.4504	$247.45	$247.45	$247.50
Purchase #2	$18.40	13.143%	$20.8183	$20.82	$20.80	$20.80
Purchase #3	$167.69	8.226%	$181.4842	$181.48	$181.50	$181.50
Purchase #4	$70.26	11.810%	$78.5577	$78.56	$78.55	$78.60
Purchase #5	$170.51	13.283%	$193.1588	$193.16	$193.15	$193.20
Purchase #6	$240.63	9.451%	$263.3719	$263.37	$263.35	$263.40
Purchase #7	$58.43	13.482%	$66.3075	$66.31	$66.30	$66.30
7 purchase totals =	$951.18		$1,051.1488	$1,051.15	$1,051.10	$1,051.30