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	$106.67	12.442%	$119.9419	$119.94	$119.95	$119.90
Purchase #2	$246.45	7.775%	$265.6115	$265.61	$265.60	$265.60
Purchase #3	$78.75	13.851%	$89.6577	$89.66	$89.65	$89.70
Purchase #4	$97.77	7.689%	$105.2875	$105.29	$105.30	$105.30
Purchase #5	$114.62	5.628%	$121.0708	$121.07	$121.05	$121.10
Purchase #6	$74.62	5.587%	$78.789	$78.79	$78.80	$78.80
Purchase #7	$165.89	9.656%	$181.9083	$181.91	$181.90	$181.90
7 purchase totals =	$884.77		$962.2667	$962.27	$962.25	$962.30