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	$157.67	7.516%	$169.5205	$169.52	$169.50	$169.50
Purchase #2	$59.50	8.576%	$64.6027	$64.60	$64.60	$64.60
Purchase #3	$230.65	8.751%	$250.8342	$250.83	$250.85	$250.80
Purchase #4	$48.81	10.296%	$53.8355	$53.84	$53.85	$53.80
Purchase #5	$99.77	3.334%	$103.0963	$103.10	$103.10	$103.10
Purchase #6	$245.33	5.390%	$258.5533	$258.55	$258.55	$258.60
Purchase #7	$10.57	9.668%	$11.5919	$11.59	$11.60	$11.60
7 purchase totals =	$852.30		$912.0344	$912.03	$912.05	$912.00