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	$201.81	8.701%	$219.3695	$219.37	$219.35	$219.40
Purchase #2	$116.57	13.201%	$131.9584	$131.96	$131.95	$132.00
Purchase #3	$168.58	13.827%	$191.8896	$191.89	$191.90	$191.90
Purchase #4	$55.48	13.345%	$62.8838	$62.88	$62.90	$62.90
Purchase #5	$45.55	8.135%	$49.2555	$49.26	$49.25	$49.30
Purchase #6	$200.70	8.511%	$217.7816	$217.78	$217.80	$217.80
Purchase #7	$33.32	12.603%	$37.5193	$37.52	$37.50	$37.50
7 purchase totals =	$822.01		$910.6577	$910.66	$910.65	$910.80