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	$47.97	4.660%	$50.2054	$50.21	$50.20	$50.20
Purchase #2	$130.78	5.259%	$137.6577	$137.66	$137.65	$137.70
Purchase #3	$186.70	5.105%	$196.231	$196.23	$196.25	$196.20
Purchase #4	$42.91	8.874%	$46.7178	$46.72	$46.70	$46.70
Purchase #5	$32.66	4.620%	$34.1689	$34.17	$34.15	$34.20
Purchase #6	$39.75	13.239%	$45.0125	$45.01	$45.00	$45.00
Purchase #7	$174.86	7.181%	$187.4167	$187.42	$187.40	$187.40
7 purchase totals =	$655.63		$697.4100	$697.42	$697.35	$697.40