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	$64.31	12.757%	$72.514	$72.51	$72.50	$72.50
Purchase #2	$187.81	12.355%	$211.0139	$211.01	$211.00	$211.00
Purchase #3	$30.82	8.606%	$33.4724	$33.47	$33.45	$33.50
Purchase #4	$5.47	8.660%	$5.9437	$5.94	$5.95	$5.90
Purchase #5	$67.85	5.186%	$71.3687	$71.37	$71.35	$71.40
Purchase #6	$49.30	4.438%	$51.4879	$51.49	$51.50	$51.50
Purchase #7	$33.61	13.824%	$38.2562	$38.26	$38.25	$38.30
7 purchase totals =	$439.17		$484.0568	$484.05	$484.00	$484.10