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	$65.90	8.832%	$71.7203	$71.72	$71.70	$71.70
Purchase #2	$17.46	4.428%	$18.2331	$18.23	$18.25	$18.20
Purchase #3	$82.95	6.500%	$88.3418	$88.34	$88.35	$88.30
Purchase #4	$212.40	4.826%	$222.6504	$222.65	$222.65	$222.70
Purchase #5	$72.38	3.378%	$74.825	$74.83	$74.85	$74.80
Purchase #6	$233.48	3.401%	$241.4207	$241.42	$241.40	$241.40
Purchase #7	$243.92	3.257%	$251.8645	$251.86	$251.85	$251.90
7 purchase totals =	$928.49		$969.0558	$969.05	$969.05	$969.00