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	$242.94	7.244%	$260.5386	$260.54	$260.55	$260.50
Purchase #2	$78.73	8.864%	$85.7086	$85.71	$85.70	$85.70
Purchase #3	$68.50	11.306%	$76.2446	$76.24	$76.25	$76.20
Purchase #4	$113.72	8.293%	$123.1508	$123.15	$123.15	$123.20
Purchase #5	$148.83	11.588%	$166.0764	$166.08	$166.10	$166.10
Purchase #6	$43.71	11.596%	$48.7786	$48.78	$48.80	$48.80
Purchase #7	$62.61	3.256%	$64.6486	$64.65	$64.65	$64.60
7 purchase totals =	$759.04		$825.1462	$825.15	$825.20	$825.10