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	$192.80	12.167%	$216.258	$216.26	$216.25	$216.30
Purchase #2	$30.35	6.300%	$32.2621	$32.26	$32.25	$32.30
Purchase #3	$125.67	12.554%	$141.4466	$141.45	$141.45	$141.40
Purchase #4	$125.96	4.258%	$131.3234	$131.32	$131.30	$131.30
Purchase #5	$129.52	13.592%	$147.1244	$147.12	$147.10	$147.10
Purchase #6	$85.54	7.327%	$91.8075	$91.81	$91.80	$91.80
Purchase #7	$121.41	13.513%	$137.8161	$137.82	$137.80	$137.80
7 purchase totals =	$811.25		$898.0381	$898.04	$897.95	$898.00