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	$93.95	7.339%	$100.845	$100.85	$100.85	$100.80
Purchase #2	$245.89	12.290%	$276.1099	$276.11	$276.10	$276.10
Purchase #3	$226.68	12.780%	$255.6497	$255.65	$255.65	$255.60
Purchase #4	$190.51	5.389%	$200.7766	$200.78	$200.80	$200.80
Purchase #5	$16.62	13.385%	$18.8446	$18.84	$18.85	$18.80
Purchase #6	$129.92	12.333%	$145.943	$145.94	$145.95	$145.90
Purchase #7	$124.37	12.120%	$139.4436	$139.44	$139.45	$139.40
7 purchase totals =	$1,027.94		$1,137.6124	$1,137.61	$1,137.65	$1,137.40