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	$10.86	8.400%	$11.7722	$11.77	$11.75	$11.80
Purchase #2	$70.99	10.231%	$78.253	$78.25	$78.25	$78.30
Purchase #3	$88.77	13.419%	$100.682	$100.68	$100.70	$100.70
Purchase #4	$202.84	12.201%	$227.5885	$227.59	$227.60	$227.60
Purchase #5	$148.75	7.168%	$159.4124	$159.41	$159.40	$159.40
Purchase #6	$44.72	12.160%	$50.158	$50.16	$50.15	$50.20
Purchase #7	$104.26	7.790%	$112.3819	$112.38	$112.40	$112.40
7 purchase totals =	$671.19		$740.2480	$740.24	$740.25	$740.40