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	$125.49	3.667%	$130.0917	$130.09	$130.10	$130.10
Purchase #2	$37.29	4.425%	$38.9401	$38.94	$38.95	$38.90
Purchase #3	$159.34	8.334%	$172.6194	$172.62	$172.60	$172.60
Purchase #4	$60.50	11.663%	$67.5561	$67.56	$67.55	$67.60
Purchase #5	$105.65	6.407%	$112.419	$112.42	$112.40	$112.40
Purchase #6	$107.43	12.258%	$120.5988	$120.60	$120.60	$120.60
Purchase #7	$121.28	7.733%	$130.6586	$130.66	$130.65	$130.70
7 purchase totals =	$716.98		$772.8837	$772.89	$772.85	$772.90