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	$159.56	8.698%	$173.4385	$173.44	$173.45	$173.40
Purchase #2	$69.96	5.726%	$73.9659	$73.97	$73.95	$74.00
Purchase #3	$37.47	7.238%	$40.1821	$40.18	$40.20	$40.20
Purchase #4	$40.35	8.616%	$43.8266	$43.83	$43.85	$43.80
Purchase #5	$197.66	9.672%	$216.7777	$216.78	$216.80	$216.80
Purchase #6	$90.49	10.835%	$100.2946	$100.29	$100.30	$100.30
Purchase #7	$141.68	12.127%	$158.8615	$158.86	$158.85	$158.90
7 purchase totals =	$737.17		$807.3469	$807.35	$807.40	$807.40