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	$72.81	13.255%	$82.461	$82.46	$82.45	$82.50
Purchase #2	$5.60	4.160%	$5.833	$5.83	$5.85	$5.80
Purchase #3	$136.82	13.361%	$155.1005	$155.10	$155.10	$155.10
Purchase #4	$132.28	13.206%	$149.7489	$149.75	$149.75	$149.70
Purchase #5	$55.72	7.248%	$59.7586	$59.76	$59.75	$59.80
Purchase #6	$55.55	8.483%	$60.2623	$60.26	$60.25	$60.30
Purchase #7	$243.95	4.873%	$255.8377	$255.84	$255.85	$255.80
7 purchase totals =	$702.73		$769.0020	$769.00	$769.00	$769.00