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	$31.46	3.664%	$32.6127	$32.61	$32.60	$32.60
Purchase #2	$50.58	13.831%	$57.5757	$57.58	$57.60	$57.60
Purchase #3	$141.75	11.865%	$158.5686	$158.57	$158.55	$158.60
Purchase #4	$113.77	3.155%	$117.3594	$117.36	$117.35	$117.40
Purchase #5	$213.81	11.752%	$238.937	$238.94	$238.95	$238.90
Purchase #6	$150.94	11.823%	$168.7856	$168.79	$168.80	$168.80
Purchase #7	$168.42	4.457%	$175.9265	$175.93	$175.95	$175.90
7 purchase totals =	$870.73		$949.7655	$949.78	$949.80	$949.80