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	$66.79	7.153%	$71.5675	$71.57	$71.55	$71.60
Purchase #2	$221.46	11.386%	$246.6754	$246.68	$246.70	$246.70
Purchase #3	$204.25	13.307%	$231.4295	$231.43	$231.45	$231.40
Purchase #4	$47.54	12.390%	$53.4302	$53.43	$53.45	$53.40
Purchase #5	$115.79	9.222%	$126.4682	$126.47	$126.45	$126.50
Purchase #6	$111.51	12.397%	$125.3339	$125.33	$125.35	$125.30
Purchase #7	$168.71	13.508%	$191.4993	$191.50	$191.50	$191.50
7 purchase totals =	$936.05		$1,046.4040	$1,046.41	$1,046.45	$1,046.40