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	$230.69	9.833%	$253.3737	$253.37	$253.35	$253.40
Purchase #2	$109.42	10.698%	$121.1258	$121.13	$121.15	$121.10
Purchase #3	$225.59	7.657%	$242.8634	$242.86	$242.85	$242.90
Purchase #4	$17.71	11.808%	$19.8012	$19.80	$19.80	$19.80
Purchase #5	$82.39	9.107%	$89.8933	$89.89	$89.90	$89.90
Purchase #6	$38.67	12.864%	$43.6445	$43.64	$43.65	$43.60
Purchase #7	$35.92	3.273%	$37.0957	$37.10	$37.10	$37.10
7 purchase totals =	$740.39		$807.7976	$807.79	$807.80	$807.80