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	$225.65	11.367%	$251.2996	$251.30	$251.30	$251.30
Purchase #2	$137.32	7.143%	$147.1288	$147.13	$147.15	$147.10
Purchase #3	$126.46	11.848%	$141.443	$141.44	$141.45	$141.40
Purchase #4	$245.27	4.113%	$255.358	$255.36	$255.35	$255.40
Purchase #5	$57.66	11.589%	$64.3422	$64.34	$64.35	$64.30
Purchase #6	$141.75	6.418%	$150.8475	$150.85	$150.85	$150.80
Purchase #7	$32.83	9.727%	$36.0234	$36.02	$36.00	$36.00
7 purchase totals =	$966.94		$1,046.4425	$1,046.44	$1,046.45	$1,046.30