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	$163.66	9.478%	$179.1717	$179.17	$179.15	$179.20
Purchase #2	$18.90	10.480%	$20.8807	$20.88	$20.90	$20.90
Purchase #3	$92.82	11.173%	$103.1908	$103.19	$103.20	$103.20
Purchase #4	$172.27	10.412%	$190.2068	$190.21	$190.20	$190.20
Purchase #5	$67.97	3.732%	$70.5066	$70.51	$70.50	$70.50
Purchase #6	$228.82	11.327%	$254.7384	$254.74	$254.75	$254.70
Purchase #7	$58.58	13.448%	$66.4578	$66.46	$66.45	$66.50
7 purchase totals =	$803.02		$885.1528	$885.16	$885.15	$885.20