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	$66.62	4.517%	$69.6292	$69.63	$69.65	$69.60
Purchase #2	$58.46	4.472%	$61.0743	$61.07	$61.05	$61.10
Purchase #3	$42.39	9.460%	$46.4001	$46.40	$46.40	$46.40
Purchase #4	$236.58	12.601%	$266.3914	$266.39	$266.40	$266.40
Purchase #5	$31.28	9.453%	$34.2369	$34.24	$34.25	$34.20
Purchase #6	$221.55	9.164%	$241.8528	$241.85	$241.85	$241.90
Purchase #7	$95.86	5.282%	$100.9233	$100.92	$100.90	$100.90
7 purchase totals =	$752.74		$820.5080	$820.50	$820.50	$820.50