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	$75.70	13.813%	$86.1564	$86.16	$86.15	$86.20
Purchase #2	$18.65	11.844%	$20.8589	$20.86	$20.85	$20.90
Purchase #3	$113.89	12.257%	$127.8495	$127.85	$127.85	$127.80
Purchase #4	$219.85	12.159%	$246.5816	$246.58	$246.60	$246.60
Purchase #5	$28.53	7.303%	$30.6135	$30.61	$30.60	$30.60
Purchase #6	$64.87	4.741%	$67.9455	$67.95	$67.95	$67.90
Purchase #7	$108.34	7.522%	$116.4893	$116.49	$116.50	$116.50
7 purchase totals =	$629.83		$696.4947	$696.50	$696.50	$696.50