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	$153.61	7.485%	$165.1077	$165.11	$165.10	$165.10
Purchase #2	$175.53	7.617%	$188.9001	$188.90	$188.90	$188.90
Purchase #3	$201.56	7.859%	$217.4006	$217.40	$217.40	$217.40
Purchase #4	$40.40	6.476%	$43.0163	$43.02	$43.00	$43.00
Purchase #5	$181.56	3.855%	$188.5591	$188.56	$188.55	$188.60
Purchase #6	$104.52	12.210%	$117.2819	$117.28	$117.30	$117.30
Purchase #7	$165.64	9.391%	$181.1953	$181.20	$181.20	$181.20
7 purchase totals =	$1,022.82		$1,101.4610	$1,101.47	$1,101.45	$1,101.50