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	$139.73	7.632%	$150.3942	$150.39	$150.40	$150.40
Purchase #2	$156.81	7.368%	$168.3638	$168.36	$168.35	$168.40
Purchase #3	$234.70	5.733%	$248.1554	$248.16	$248.15	$248.20
Purchase #4	$168.56	10.319%	$185.9537	$185.95	$185.95	$186.00
Purchase #5	$231.99	8.212%	$251.041	$251.04	$251.05	$251.00
Purchase #6	$93.57	7.827%	$100.8937	$100.89	$100.90	$100.90
Purchase #7	$231.38	10.136%	$254.8327	$254.83	$254.85	$254.80
7 purchase totals =	$1,256.74		$1,359.6345	$1,359.62	$1,359.65	$1,359.70