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	$104.91	11.480%	$116.9537	$116.95	$116.95	$117.00
Purchase #2	$39.98	13.527%	$45.3881	$45.39	$45.40	$45.40
Purchase #3	$196.33	5.148%	$206.4371	$206.44	$206.45	$206.40
Purchase #4	$30.49	8.239%	$33.0021	$33.00	$33.00	$33.00
Purchase #5	$56.89	10.621%	$62.9323	$62.93	$62.95	$62.90
Purchase #6	$101.87	3.201%	$105.1309	$105.13	$105.15	$105.10
Purchase #7	$165.41	4.548%	$172.9328	$172.93	$172.95	$172.90
7 purchase totals =	$695.88		$742.7770	$742.77	$742.85	$742.70