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	$148.99	4.651%	$155.9195	$155.92	$155.90	$155.90
Purchase #2	$28.56	12.108%	$32.018	$32.02	$32.00	$32.00
Purchase #3	$121.53	4.272%	$126.7218	$126.72	$126.70	$126.70
Purchase #4	$60.27	6.605%	$64.2508	$64.25	$64.25	$64.30
Purchase #5	$52.40	13.733%	$59.5961	$59.60	$59.60	$59.60
Purchase #6	$61.54	4.778%	$64.4804	$64.48	$64.50	$64.50
Purchase #7	$213.72	6.149%	$226.8616	$226.86	$226.85	$226.90
7 purchase totals =	$687.01		$729.8482	$729.85	$729.80	$729.90