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	$241.52	11.760%	$269.9228	$269.92	$269.90	$269.90
Purchase #2	$185.89	12.105%	$208.392	$208.39	$208.40	$208.40
Purchase #3	$95.51	5.278%	$100.551	$100.55	$100.55	$100.60
Purchase #4	$129.54	10.637%	$143.3192	$143.32	$143.30	$143.30
Purchase #5	$189.53	10.636%	$209.6884	$209.69	$209.70	$209.70
Purchase #6	$80.71	13.222%	$91.3815	$91.38	$91.40	$91.40
Purchase #7	$28.78	13.283%	$32.6028	$32.60	$32.60	$32.60
7 purchase totals =	$951.48		$1,055.8577	$1,055.85	$1,055.85	$1,055.90