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	$129.48	9.511%	$141.7948	$141.79	$141.80	$141.80
Purchase #2	$48.55	4.484%	$50.727	$50.73	$50.75	$50.70
Purchase #3	$155.48	13.131%	$175.8961	$175.90	$175.90	$175.90
Purchase #4	$72.97	5.621%	$77.0716	$77.07	$77.05	$77.10
Purchase #5	$63.82	3.121%	$65.8118	$65.81	$65.80	$65.80
Purchase #6	$111.96	13.571%	$127.1541	$127.15	$127.15	$127.20
Purchase #7	$36.45	8.168%	$39.4272	$39.43	$39.45	$39.40
7 purchase totals =	$618.71		$677.8826	$677.88	$677.90	$677.90