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	$176.57	13.720%	$200.7954	$200.80	$200.80	$200.80
Purchase #2	$178.67	7.801%	$192.608	$192.61	$192.60	$192.60
Purchase #3	$100.47	6.354%	$106.8539	$106.85	$106.85	$106.90
Purchase #4	$92.63	11.318%	$103.1139	$103.11	$103.10	$103.10
Purchase #5	$81.51	9.858%	$89.5453	$89.55	$89.55	$89.50
Purchase #6	$135.81	11.870%	$151.9306	$151.93	$151.95	$151.90
Purchase #7	$97.46	12.487%	$109.6298	$109.63	$109.65	$109.60
7 purchase totals =	$863.12		$954.4769	$954.48	$954.50	$954.40