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	$244.26	9.848%	$268.3147	$268.31	$268.30	$268.30
Purchase #2	$140.63	13.118%	$159.0778	$159.08	$159.10	$159.10
Purchase #3	$24.47	10.511%	$27.042	$27.04	$27.05	$27.00
Purchase #4	$194.39	11.506%	$216.7565	$216.76	$216.75	$216.80
Purchase #5	$90.87	10.733%	$100.6231	$100.62	$100.60	$100.60
Purchase #6	$241.85	13.496%	$274.4901	$274.49	$274.50	$274.50
Purchase #7	$125.38	6.833%	$133.9472	$133.95	$133.95	$133.90
7 purchase totals =	$1,061.85		$1,180.2514	$1,180.25	$1,180.25	$1,180.20