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	$105.68	10.284%	$116.5481	$116.55	$116.55	$116.50
Purchase #2	$92.38	8.483%	$100.2166	$100.22	$100.20	$100.20
Purchase #3	$17.69	4.618%	$18.5069	$18.51	$18.50	$18.50
Purchase #4	$44.34	10.468%	$48.9815	$48.98	$49.00	$49.00
Purchase #5	$35.72	12.454%	$40.1686	$40.17	$40.15	$40.20
Purchase #6	$93.58	8.521%	$101.554	$101.55	$101.55	$101.60
Purchase #7	$26.35	9.504%	$28.8543	$28.85	$28.85	$28.90
7 purchase totals =	$415.74		$454.8300	$454.83	$454.80	$454.90