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	$40.47	12.828%	$45.6615	$45.66	$45.65	$45.70
Purchase #2	$181.39	10.207%	$199.9045	$199.90	$199.90	$199.90
Purchase #3	$9.93	5.243%	$10.4506	$10.45	$10.45	$10.50
Purchase #4	$50.94	7.249%	$54.6326	$54.63	$54.65	$54.60
Purchase #5	$59.94	7.710%	$64.5614	$64.56	$64.55	$64.60
Purchase #6	$35.77	9.487%	$39.1635	$39.16	$39.15	$39.20
Purchase #7	$135.50	12.874%	$152.9443	$152.94	$152.95	$152.90
7 purchase totals =	$513.94		$567.3184	$567.30	$567.30	$567.40