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	$116.51	10.639%	$128.9055	$128.91	$128.90	$128.90
Purchase #2	$164.33	5.648%	$173.6114	$173.61	$173.60	$173.60
Purchase #3	$60.63	7.314%	$65.0645	$65.06	$65.05	$65.10
Purchase #4	$116.89	5.190%	$122.9566	$122.96	$122.95	$123.00
Purchase #5	$140.30	13.677%	$159.4888	$159.49	$159.50	$159.50
Purchase #6	$139.88	8.694%	$152.0412	$152.04	$152.05	$152.00
Purchase #7	$198.78	8.799%	$216.2707	$216.27	$216.25	$216.30
7 purchase totals =	$937.32		$1,018.3387	$1,018.34	$1,018.30	$1,018.40