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	$9.96	13.391%	$11.2937	$11.29	$11.30	$11.30
Purchase #2	$228.56	8.149%	$247.1854	$247.19	$247.20	$247.20
Purchase #3	$62.52	11.401%	$69.6479	$69.65	$69.65	$69.60
Purchase #4	$137.59	6.512%	$146.5499	$146.55	$146.55	$146.50
Purchase #5	$156.72	7.484%	$168.4489	$168.45	$168.45	$168.40
Purchase #6	$143.63	8.452%	$155.7696	$155.77	$155.75	$155.80
Purchase #7	$231.55	10.819%	$256.6014	$256.60	$256.60	$256.60
7 purchase totals =	$970.53		$1,055.4968	$1,055.50	$1,055.50	$1,055.40