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	$47.91	8.764%	$52.1088	$52.11	$52.10	$52.10
Purchase #2	$110.93	10.229%	$122.277	$122.28	$122.30	$122.30
Purchase #3	$125.45	11.261%	$139.5769	$139.58	$139.60	$139.60
Purchase #4	$182.46	12.539%	$205.3387	$205.34	$205.35	$205.30
Purchase #5	$93.79	6.627%	$100.0055	$100.01	$100.00	$100.00
Purchase #6	$156.53	3.565%	$162.1103	$162.11	$162.10	$162.10
Purchase #7	$105.72	7.690%	$113.8499	$113.85	$113.85	$113.80
7 purchase totals =	$822.79		$895.2671	$895.28	$895.30	$895.20