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	$10.44	10.312%	$11.5166	$11.52	$11.50	$11.50
Purchase #2	$19.63	4.598%	$20.5326	$20.53	$20.55	$20.50
Purchase #3	$37.64	6.709%	$40.1653	$40.17	$40.15	$40.20
Purchase #4	$93.37	10.479%	$103.1542	$103.15	$103.15	$103.20
Purchase #5	$76.66	8.460%	$83.1454	$83.15	$83.15	$83.10
Purchase #6	$86.53	6.344%	$92.0195	$92.02	$92.00	$92.00
Purchase #7	$56.47	13.824%	$64.2764	$64.28	$64.30	$64.30
7 purchase totals =	$380.74		$414.8100	$414.82	$414.80	$414.80