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	$158.73	8.653%	$172.4649	$172.46	$172.45	$172.50
Purchase #2	$29.49	6.492%	$31.4045	$31.40	$31.40	$31.40
Purchase #3	$63.81	12.655%	$71.8852	$71.89	$71.90	$71.90
Purchase #4	$117.35	4.330%	$122.4313	$122.43	$122.45	$122.40
Purchase #5	$212.74	4.806%	$222.9643	$222.96	$222.95	$223.00
Purchase #6	$136.73	11.544%	$152.5141	$152.51	$152.50	$152.50
Purchase #7	$178.91	5.196%	$188.2062	$188.21	$188.20	$188.20
7 purchase totals =	$897.76		$961.8705	$961.86	$961.85	$961.90