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	$78.53	10.815%	$87.023	$87.02	$87.00	$87.00
Purchase #2	$13.80	12.439%	$15.5166	$15.52	$15.50	$15.50
Purchase #3	$142.56	3.325%	$147.3001	$147.30	$147.30	$147.30
Purchase #4	$206.70	12.778%	$233.1121	$233.11	$233.10	$233.10
Purchase #5	$140.42	7.870%	$151.4711	$151.47	$151.45	$151.50
Purchase #6	$169.79	9.250%	$185.4956	$185.50	$185.50	$185.50
Purchase #7	$146.85	12.852%	$165.7232	$165.72	$165.70	$165.70
7 purchase totals =	$898.65		$985.6417	$985.64	$985.55	$985.60