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	$33.83	9.841%	$37.1592	$37.16	$37.15	$37.20
Purchase #2	$22.51	10.512%	$24.8763	$24.88	$24.90	$24.90
Purchase #3	$105.49	6.678%	$112.5346	$112.53	$112.55	$112.50
Purchase #4	$77.77	5.731%	$82.227	$82.23	$82.25	$82.20
Purchase #5	$99.61	12.452%	$112.0134	$112.01	$112.00	$112.00
Purchase #6	$248.49	3.276%	$256.6305	$256.63	$256.65	$256.60
Purchase #7	$181.70	10.198%	$200.2298	$200.23	$200.25	$200.20
7 purchase totals =	$769.40		$825.6708	$825.67	$825.75	$825.60