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	$87.71	6.335%	$93.2664	$93.27	$93.25	$93.30
Purchase #2	$11.41	10.466%	$12.6042	$12.60	$12.60	$12.60
Purchase #3	$184.61	8.460%	$200.228	$200.23	$200.25	$200.20
Purchase #4	$37.67	7.520%	$40.5028	$40.50	$40.50	$40.50
Purchase #5	$58.33	4.588%	$61.0062	$61.01	$61.00	$61.00
Purchase #6	$158.51	6.707%	$169.1413	$169.14	$169.15	$169.10
Purchase #7	$190.61	11.228%	$212.0117	$212.01	$212.00	$212.00
7 purchase totals =	$728.85		$788.7606	$788.76	$788.75	$788.70