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	$168.53	3.140%	$173.8218	$173.82	$173.80	$173.80
Purchase #2	$230.29	13.738%	$261.9272	$261.93	$261.95	$261.90
Purchase #3	$198.48	4.243%	$206.9015	$206.90	$206.90	$206.90
Purchase #4	$169.78	5.564%	$179.2266	$179.23	$179.25	$179.20
Purchase #5	$32.87	7.863%	$35.4546	$35.45	$35.45	$35.50
Purchase #6	$81.95	11.133%	$91.0735	$91.07	$91.05	$91.10
Purchase #7	$130.33	4.819%	$136.6106	$136.61	$136.60	$136.60
7 purchase totals =	$1,012.23		$1,085.0158	$1,085.01	$1,085.00	$1,085.00