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	$45.84	5.422%	$48.3254	$48.33	$48.35	$48.30
Purchase #2	$42.46	3.504%	$43.9478	$43.95	$43.95	$43.90
Purchase #3	$99.29	3.865%	$103.1276	$103.13	$103.15	$103.10
Purchase #4	$52.49	8.873%	$57.1474	$57.15	$57.15	$57.10
Purchase #5	$22.65	13.790%	$25.7734	$25.77	$25.75	$25.80
Purchase #6	$64.53	10.448%	$71.2721	$71.27	$71.25	$71.30
Purchase #7	$137.83	4.620%	$144.1977	$144.20	$144.20	$144.20
7 purchase totals =	$465.09		$493.7914	$493.80	$493.80	$493.70