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	$62.69	6.634%	$66.8489	$66.85	$66.85	$66.80
Purchase #2	$92.40	11.718%	$103.2274	$103.23	$103.25	$103.20
Purchase #3	$129.66	5.219%	$136.427	$136.43	$136.45	$136.40
Purchase #4	$9.36	11.194%	$10.4078	$10.41	$10.40	$10.40
Purchase #5	$197.33	6.621%	$210.3952	$210.40	$210.40	$210.40
Purchase #6	$152.56	10.343%	$168.3393	$168.34	$168.35	$168.30
Purchase #7	$64.78	4.391%	$67.6245	$67.62	$67.60	$67.60
7 purchase totals =	$708.78		$763.2701	$763.28	$763.30	$763.10