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	$42.27	7.873%	$45.5979	$45.60	$45.60	$45.60
Purchase #2	$208.82	11.386%	$232.5962	$232.60	$232.60	$232.60
Purchase #3	$99.85	3.321%	$103.166	$103.17	$103.15	$103.20
Purchase #4	$239.32	7.239%	$256.6444	$256.64	$256.65	$256.60
Purchase #5	$31.27	11.238%	$34.7841	$34.78	$34.80	$34.80
Purchase #6	$129.89	10.597%	$143.6544	$143.65	$143.65	$143.70
Purchase #7	$96.93	5.369%	$102.1342	$102.13	$102.15	$102.10
7 purchase totals =	$848.35		$918.5772	$918.57	$918.60	$918.60