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	$120.93	8.380%	$131.0639	$131.06	$131.05	$131.10
Purchase #2	$127.94	7.780%	$137.8937	$137.89	$137.90	$137.90
Purchase #3	$82.58	5.805%	$87.3738	$87.37	$87.35	$87.40
Purchase #4	$49.62	9.753%	$54.4594	$54.46	$54.45	$54.50
Purchase #5	$219.99	11.146%	$244.5101	$244.51	$244.50	$244.50
Purchase #6	$10.91	5.508%	$11.5109	$11.51	$11.50	$11.50
Purchase #7	$68.67	13.119%	$77.6788	$77.68	$77.70	$77.70
7 purchase totals =	$680.64		$744.4906	$744.48	$744.45	$744.60