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	$60.57	5.282%	$63.7693	$63.77	$63.75	$63.80
Purchase #2	$166.43	11.628%	$185.7825	$185.78	$185.80	$185.80
Purchase #3	$61.57	12.604%	$69.3303	$69.33	$69.35	$69.30
Purchase #4	$139.52	7.762%	$150.3495	$150.35	$150.35	$150.30
Purchase #5	$230.43	11.404%	$256.7082	$256.71	$256.70	$256.70
Purchase #6	$24.97	3.544%	$25.8549	$25.85	$25.85	$25.90
Purchase #7	$32.88	4.733%	$34.4362	$34.44	$34.45	$34.40
7 purchase totals =	$716.37		$786.2309	$786.23	$786.25	$786.20