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	$199.44	7.274%	$213.9473	$213.95	$213.95	$213.90
Purchase #2	$127.64	13.540%	$144.9225	$144.92	$144.90	$144.90
Purchase #3	$182.88	8.628%	$198.6589	$198.66	$198.65	$198.70
Purchase #4	$86.78	3.445%	$89.7696	$89.77	$89.75	$89.80
Purchase #5	$204.43	12.298%	$229.5708	$229.57	$229.55	$229.60
Purchase #6	$250.48	3.724%	$259.8079	$259.81	$259.80	$259.80
Purchase #7	$109.43	9.644%	$119.9834	$119.98	$120.00	$120.00
7 purchase totals =	$1,161.08		$1,256.6604	$1,256.66	$1,256.60	$1,256.70