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	$95.78	8.475%	$103.8974	$103.90	$103.90	$103.90
Purchase #2	$206.27	8.282%	$223.3533	$223.35	$223.35	$223.40
Purchase #3	$203.78	7.487%	$219.037	$219.04	$219.05	$219.00
Purchase #4	$24.58	11.733%	$27.464	$27.46	$27.45	$27.50
Purchase #5	$118.81	8.803%	$129.2688	$129.27	$129.25	$129.30
Purchase #6	$36.39	5.759%	$38.4857	$38.49	$38.50	$38.50
Purchase #7	$135.91	11.334%	$151.314	$151.31	$151.30	$151.30
7 purchase totals =	$821.52		$892.8202	$892.82	$892.80	$892.90