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	$157.64	5.485%	$166.2866	$166.29	$166.30	$166.30
Purchase #2	$87.42	13.831%	$99.5111	$99.51	$99.50	$99.50
Purchase #3	$33.61	11.628%	$37.5182	$37.52	$37.50	$37.50
Purchase #4	$55.69	8.217%	$60.266	$60.27	$60.25	$60.30
Purchase #5	$160.42	13.611%	$182.2548	$182.25	$182.25	$182.30
Purchase #6	$8.86	8.189%	$9.5855	$9.59	$9.60	$9.60
Purchase #7	$130.80	6.804%	$139.6996	$139.70	$139.70	$139.70
7 purchase totals =	$634.44		$695.1218	$695.13	$695.10	$695.20