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	$113.93	11.782%	$127.3532	$127.35	$127.35	$127.40
Purchase #2	$102.68	10.824%	$113.7941	$113.79	$113.80	$113.80
Purchase #3	$33.72	11.174%	$37.4879	$37.49	$37.50	$37.50
Purchase #4	$111.72	11.659%	$124.7454	$124.75	$124.75	$124.70
Purchase #5	$34.84	6.122%	$36.9729	$36.97	$36.95	$37.00
Purchase #6	$152.37	13.233%	$172.5331	$172.53	$172.55	$172.50
Purchase #7	$136.82	9.122%	$149.3007	$149.30	$149.30	$149.30
7 purchase totals =	$686.08		$762.1873	$762.18	$762.20	$762.20