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	$198.54	13.387%	$225.1185	$225.12	$225.10	$225.10
Purchase #2	$149.63	7.266%	$160.5021	$160.50	$160.50	$160.50
Purchase #3	$248.52	12.418%	$279.3812	$279.38	$279.40	$279.40
Purchase #4	$172.49	10.439%	$190.4962	$190.50	$190.50	$190.50
Purchase #5	$192.48	6.644%	$205.2684	$205.27	$205.25	$205.30
Purchase #6	$26.53	5.852%	$28.0825	$28.08	$28.10	$28.10
Purchase #7	$95.82	10.540%	$105.9194	$105.92	$105.90	$105.90
7 purchase totals =	$1,084.01		$1,194.7683	$1,194.77	$1,194.75	$1,194.80