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	$225.59	8.833%	$245.5164	$245.52	$245.50	$245.50
Purchase #2	$38.97	8.556%	$42.3043	$42.30	$42.30	$42.30
Purchase #3	$10.55	12.397%	$11.8579	$11.86	$11.85	$11.90
Purchase #4	$218.96	3.137%	$225.8288	$225.83	$225.85	$225.80
Purchase #5	$72.70	12.480%	$81.773	$81.77	$81.75	$81.80
Purchase #6	$68.31	4.398%	$71.3143	$71.31	$71.30	$71.30
Purchase #7	$102.46	13.852%	$116.6528	$116.65	$116.65	$116.70
7 purchase totals =	$737.54		$795.2475	$795.24	$795.20	$795.30