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	$126.83	10.763%	$140.4807	$140.48	$140.50	$140.50
Purchase #2	$195.88	13.805%	$222.9212	$222.92	$222.90	$222.90
Purchase #3	$230.76	11.107%	$256.3905	$256.39	$256.40	$256.40
Purchase #4	$154.51	11.403%	$172.1288	$172.13	$172.15	$172.10
Purchase #5	$194.54	6.269%	$206.7357	$206.74	$206.75	$206.70
Purchase #6	$116.67	13.248%	$132.1264	$132.13	$132.15	$132.10
Purchase #7	$126.73	13.123%	$143.3608	$143.36	$143.35	$143.40
7 purchase totals =	$1,145.92		$1,274.1441	$1,274.15	$1,274.20	$1,274.10