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	$33.72	8.196%	$36.4837	$36.48	$36.50	$36.50
Purchase #2	$93.45	7.173%	$100.1532	$100.15	$100.15	$100.20
Purchase #3	$53.91	11.731%	$60.2342	$60.23	$60.25	$60.20
Purchase #4	$60.76	12.369%	$68.2754	$68.28	$68.30	$68.30
Purchase #5	$195.51	11.164%	$217.3367	$217.34	$217.35	$217.30
Purchase #6	$40.57	3.699%	$42.0707	$42.07	$42.05	$42.10
Purchase #7	$114.79	11.141%	$127.5788	$127.58	$127.60	$127.60
7 purchase totals =	$592.71		$652.1327	$652.13	$652.20	$652.20