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	$234.89	8.375%	$254.562	$254.56	$254.55	$254.60
Purchase #2	$103.27	9.694%	$113.281	$113.28	$113.30	$113.30
Purchase #3	$110.29	8.461%	$119.6216	$119.62	$119.60	$119.60
Purchase #4	$152.34	13.197%	$172.4443	$172.44	$172.45	$172.40
Purchase #5	$57.39	3.866%	$59.6087	$59.61	$59.60	$59.60
Purchase #6	$14.52	8.868%	$15.8076	$15.81	$15.80	$15.80
Purchase #7	$36.63	9.814%	$40.2249	$40.22	$40.20	$40.20
7 purchase totals =	$709.33		$775.5501	$775.54	$775.50	$775.50