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	$195.41	7.154%	$209.3896	$209.39	$209.40	$209.40
Purchase #2	$202.28	10.168%	$222.8478	$222.85	$222.85	$222.80
Purchase #3	$117.33	7.340%	$125.942	$125.94	$125.95	$125.90
Purchase #4	$121.38	13.600%	$137.8877	$137.89	$137.90	$137.90
Purchase #5	$145.33	4.639%	$152.0719	$152.07	$152.05	$152.10
Purchase #6	$37.51	7.748%	$40.4163	$40.42	$40.40	$40.40
Purchase #7	$52.76	3.586%	$54.652	$54.65	$54.65	$54.70
7 purchase totals =	$872.00		$943.2073	$943.21	$943.20	$943.20