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	$208.38	4.503%	$217.7634	$217.76	$217.75	$217.80
Purchase #2	$209.58	7.777%	$225.879	$225.88	$225.90	$225.90
Purchase #3	$126.37	11.859%	$141.3562	$141.36	$141.35	$141.40
Purchase #4	$42.70	7.385%	$45.8534	$45.85	$45.85	$45.90
Purchase #5	$164.74	10.371%	$181.8252	$181.83	$181.85	$181.80
Purchase #6	$247.32	8.389%	$268.0677	$268.07	$268.05	$268.10
Purchase #7	$83.31	9.149%	$90.932	$90.93	$90.95	$90.90
7 purchase totals =	$1,082.40		$1,171.6769	$1,171.68	$1,171.70	$1,171.80