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	$50.33	3.242%	$51.9617	$51.96	$51.95	$52.00
Purchase #2	$175.50	13.525%	$199.2364	$199.24	$199.25	$199.20
Purchase #3	$197.85	11.761%	$221.1191	$221.12	$221.10	$221.10
Purchase #4	$165.72	4.264%	$172.7863	$172.79	$172.80	$172.80
Purchase #5	$36.51	9.266%	$39.893	$39.89	$39.90	$39.90
Purchase #6	$47.74	13.213%	$54.0479	$54.05	$54.05	$54.00
Purchase #7	$58.46	10.429%	$64.5568	$64.56	$64.55	$64.60
7 purchase totals =	$732.11		$803.6012	$803.61	$803.60	$803.60