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	$202.80	6.788%	$216.5661	$216.57	$216.55	$216.60
Purchase #2	$35.87	12.802%	$40.4621	$40.46	$40.45	$40.50
Purchase #3	$138.71	10.828%	$153.7295	$153.73	$153.75	$153.70
Purchase #4	$243.57	7.331%	$261.4261	$261.43	$261.45	$261.40
Purchase #5	$190.87	13.466%	$216.5726	$216.57	$216.55	$216.60
Purchase #6	$64.85	13.723%	$73.7494	$73.75	$73.75	$73.70
Purchase #7	$18.49	12.766%	$20.8504	$20.85	$20.85	$20.90
7 purchase totals =	$895.16		$983.3562	$983.36	$983.35	$983.40