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	$189.44	6.661%	$202.0586	$202.06	$202.05	$202.10
Purchase #2	$38.54	5.770%	$40.7638	$40.76	$40.75	$40.80
Purchase #3	$153.43	3.141%	$158.2492	$158.25	$158.25	$158.20
Purchase #4	$45.51	6.459%	$48.4495	$48.45	$48.45	$48.40
Purchase #5	$137.83	6.183%	$146.352	$146.35	$146.35	$146.40
Purchase #6	$233.54	4.195%	$243.337	$243.34	$243.35	$243.30
Purchase #7	$111.83	10.791%	$123.8976	$123.90	$123.90	$123.90
7 purchase totals =	$910.12		$963.1077	$963.11	$963.10	$963.10