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	$46.73	7.783%	$50.367	$50.37	$50.35	$50.40
Purchase #2	$195.59	13.289%	$221.582	$221.58	$221.60	$221.60
Purchase #3	$6.59	9.318%	$7.2041	$7.20	$7.20	$7.20
Purchase #4	$48.40	8.136%	$52.3378	$52.34	$52.35	$52.30
Purchase #5	$103.54	8.475%	$112.315	$112.32	$112.30	$112.30
Purchase #6	$172.52	9.565%	$189.0215	$189.02	$189.00	$189.00
Purchase #7	$71.79	9.634%	$78.7062	$78.71	$78.70	$78.70
7 purchase totals =	$645.16		$711.5336	$711.54	$711.50	$711.50