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	$146.89	13.712%	$167.0316	$167.03	$167.05	$167.00
Purchase #2	$83.85	10.754%	$92.8672	$92.87	$92.85	$92.90
Purchase #3	$35.71	8.588%	$38.7768	$38.78	$38.80	$38.80
Purchase #4	$6.80	8.486%	$7.377	$7.38	$7.40	$7.40
Purchase #5	$154.46	3.401%	$159.7132	$159.71	$159.70	$159.70
Purchase #6	$234.93	3.232%	$242.5229	$242.52	$242.50	$242.50
Purchase #7	$201.86	3.824%	$209.5791	$209.58	$209.60	$209.60
7 purchase totals =	$864.50		$917.8678	$917.87	$917.90	$917.90