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	$77.35	10.675%	$85.6071	$85.61	$85.60	$85.60
Purchase #2	$105.71	4.624%	$110.598	$110.60	$110.60	$110.60
Purchase #3	$238.39	6.741%	$254.4599	$254.46	$254.45	$254.50
Purchase #4	$213.79	10.556%	$236.3577	$236.36	$236.35	$236.40
Purchase #5	$46.61	8.132%	$50.4003	$50.40	$50.40	$50.40
Purchase #6	$31.80	11.792%	$35.5499	$35.55	$35.55	$35.50
Purchase #7	$137.69	6.659%	$146.8588	$146.86	$146.85	$146.90
7 purchase totals =	$851.34		$919.8317	$919.84	$919.80	$919.90