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	$77.70	4.645%	$81.3092	$81.31	$81.30	$81.30
Purchase #2	$246.68	13.727%	$280.5418	$280.54	$280.55	$280.50
Purchase #3	$55.42	7.304%	$59.4679	$59.47	$59.45	$59.50
Purchase #4	$188.78	4.728%	$197.7055	$197.71	$197.70	$197.70
Purchase #5	$124.91	12.793%	$140.8897	$140.89	$140.90	$140.90
Purchase #6	$62.96	11.485%	$70.191	$70.19	$70.20	$70.20
Purchase #7	$238.56	13.575%	$270.9445	$270.94	$270.95	$270.90
7 purchase totals =	$995.01		$1,101.0496	$1,101.05	$1,101.05	$1,101.00