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	$163.70	13.519%	$185.8306	$185.83	$185.85	$185.80
Purchase #2	$137.55	13.112%	$155.5856	$155.59	$155.60	$155.60
Purchase #3	$92.74	3.408%	$95.9006	$95.90	$95.90	$95.90
Purchase #4	$116.89	5.843%	$123.7199	$123.72	$123.70	$123.70
Purchase #5	$50.76	6.384%	$54.0005	$54.00	$54.00	$54.00
Purchase #6	$205.79	13.860%	$234.3125	$234.31	$234.30	$234.30
Purchase #7	$177.34	8.634%	$192.6515	$192.65	$192.65	$192.70
7 purchase totals =	$944.77		$1,042.0012	$1,042.00	$1,042.00	$1,042.00