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	$113.73	9.637%	$124.6902	$124.69	$124.70	$124.70
Purchase #2	$76.98	6.723%	$82.1554	$82.16	$82.15	$82.20
Purchase #3	$131.88	6.673%	$140.6804	$140.68	$140.70	$140.70
Purchase #4	$37.79	7.403%	$40.5876	$40.59	$40.60	$40.60
Purchase #5	$87.48	3.733%	$90.7456	$90.75	$90.75	$90.70
Purchase #6	$52.94	3.117%	$54.5901	$54.59	$54.60	$54.60
Purchase #7	$202.89	6.174%	$215.4164	$215.42	$215.40	$215.40
7 purchase totals =	$703.69		$748.8657	$748.88	$748.90	$748.90