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	$155.71	12.738%	$175.5443	$175.54	$175.55	$175.50
Purchase #2	$6.78	8.232%	$7.3381	$7.34	$7.35	$7.30
Purchase #3	$35.61	5.226%	$37.471	$37.47	$37.45	$37.50
Purchase #4	$119.45	6.236%	$126.8989	$126.90	$126.90	$126.90
Purchase #5	$132.71	13.416%	$150.5144	$150.51	$150.50	$150.50
Purchase #6	$72.88	5.269%	$76.72	$76.72	$76.70	$76.70
Purchase #7	$107.68	9.508%	$117.9182	$117.92	$117.90	$117.90
7 purchase totals =	$630.82		$692.4049	$692.40	$692.35	$692.30