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	$210.38	13.429%	$238.6319	$238.63	$238.65	$238.60
Purchase #2	$11.40	10.696%	$12.6193	$12.62	$12.60	$12.60
Purchase #3	$157.56	13.520%	$178.8621	$178.86	$178.85	$178.90
Purchase #4	$30.85	13.384%	$34.979	$34.98	$35.00	$35.00
Purchase #5	$69.81	4.369%	$72.86	$72.86	$72.85	$72.90
Purchase #6	$122.61	3.690%	$127.1343	$127.13	$127.15	$127.10
Purchase #7	$44.58	12.851%	$50.309	$50.31	$50.30	$50.30
7 purchase totals =	$647.19		$715.3956	$715.39	$715.40	$715.40