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	$217.82	12.350%	$244.7208	$244.72	$244.70	$244.70
Purchase #2	$136.61	12.523%	$153.7177	$153.72	$153.70	$153.70
Purchase #3	$43.56	13.636%	$49.4998	$49.50	$49.50	$49.50
Purchase #4	$13.96	11.601%	$15.5795	$15.58	$15.60	$15.60
Purchase #5	$92.92	4.736%	$97.3207	$97.32	$97.30	$97.30
Purchase #6	$79.95	3.140%	$82.4604	$82.46	$82.45	$82.50
Purchase #7	$159.39	3.282%	$164.6212	$164.62	$164.60	$164.60
7 purchase totals =	$744.21		$807.9201	$807.92	$807.85	$807.90