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	$56.65	11.211%	$63.001	$63.00	$63.00	$63.00
Purchase #2	$148.43	7.443%	$159.4776	$159.48	$159.50	$159.50
Purchase #3	$49.39	10.705%	$54.6772	$54.68	$54.70	$54.70
Purchase #4	$124.80	12.363%	$140.229	$140.23	$140.25	$140.20
Purchase #5	$22.90	11.311%	$25.4902	$25.49	$25.50	$25.50
Purchase #6	$55.78	7.354%	$59.8821	$59.88	$59.90	$59.90
Purchase #7	$61.25	6.456%	$65.2043	$65.20	$65.20	$65.20
7 purchase totals =	$519.20		$567.9614	$567.96	$568.05	$568.00