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	$40.41	9.644%	$44.3071	$44.31	$44.30	$44.30
Purchase #2	$34.61	13.617%	$39.3228	$39.32	$39.30	$39.30
Purchase #3	$244.42	4.700%	$255.9077	$255.91	$255.90	$255.90
Purchase #4	$71.38	12.170%	$80.0669	$80.07	$80.05	$80.10
Purchase #5	$175.66	4.216%	$183.0658	$183.07	$183.05	$183.10
Purchase #6	$49.58	4.429%	$51.7759	$51.78	$51.80	$51.80
Purchase #7	$55.31	5.738%	$58.4837	$58.48	$58.50	$58.50
7 purchase totals =	$671.37		$712.9299	$712.94	$712.90	$713.00