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	$98.84	13.581%	$112.2635	$112.26	$112.25	$112.30
Purchase #2	$151.94	3.851%	$157.7912	$157.79	$157.80	$157.80
Purchase #3	$42.26	8.261%	$45.7511	$45.75	$45.75	$45.80
Purchase #4	$91.27	10.137%	$100.522	$100.52	$100.50	$100.50
Purchase #5	$132.40	8.589%	$143.7718	$143.77	$143.75	$143.80
Purchase #6	$64.37	9.488%	$70.4774	$70.48	$70.50	$70.50
Purchase #7	$154.35	7.344%	$165.6855	$165.69	$165.70	$165.70
7 purchase totals =	$735.43		$796.2625	$796.26	$796.25	$796.40