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	$119.45	3.258%	$123.3417	$123.34	$123.35	$123.30
Purchase #2	$102.77	5.680%	$108.6073	$108.61	$108.60	$108.60
Purchase #3	$115.69	8.501%	$125.5248	$125.52	$125.50	$125.50
Purchase #4	$18.60	3.691%	$19.2865	$19.29	$19.30	$19.30
Purchase #5	$79.47	3.766%	$82.4628	$82.46	$82.45	$82.50
Purchase #6	$211.31	7.760%	$227.7077	$227.71	$227.70	$227.70
Purchase #7	$174.90	11.862%	$195.6466	$195.65	$195.65	$195.60
7 purchase totals =	$822.19		$882.5774	$882.58	$882.55	$882.50