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	$203.65	13.590%	$231.326	$231.33	$231.35	$231.30
Purchase #2	$7.34	3.653%	$7.6081	$7.61	$7.60	$7.60
Purchase #3	$209.75	3.849%	$217.8233	$217.82	$217.80	$217.80
Purchase #4	$110.60	3.581%	$114.5606	$114.56	$114.55	$114.60
Purchase #5	$143.48	10.724%	$158.8668	$158.87	$158.85	$158.90
Purchase #6	$51.86	13.490%	$58.8559	$58.86	$58.85	$58.90
Purchase #7	$176.50	7.306%	$189.3951	$189.40	$189.40	$189.40
7 purchase totals =	$903.18		$978.4358	$978.45	$978.40	$978.50