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	$64.60	5.770%	$68.3274	$68.33	$68.35	$68.30
Purchase #2	$116.51	5.617%	$123.0544	$123.05	$123.05	$123.10
Purchase #3	$248.57	11.255%	$276.5466	$276.55	$276.55	$276.50
Purchase #4	$43.57	11.660%	$48.6503	$48.65	$48.65	$48.70
Purchase #5	$233.43	12.588%	$262.8142	$262.81	$262.80	$262.80
Purchase #6	$120.54	9.306%	$131.7575	$131.76	$131.75	$131.80
Purchase #7	$190.38	13.477%	$216.0375	$216.04	$216.05	$216.00
7 purchase totals =	$1,017.60		$1,127.1879	$1,127.19	$1,127.20	$1,127.20