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	$203.94	4.674%	$213.4722	$213.47	$213.45	$213.50
Purchase #2	$74.97	4.816%	$78.5806	$78.58	$78.60	$78.60
Purchase #3	$35.46	6.342%	$37.7089	$37.71	$37.70	$37.70
Purchase #4	$146.25	10.538%	$161.6618	$161.66	$161.65	$161.70
Purchase #5	$13.85	7.867%	$14.9396	$14.94	$14.95	$14.90
Purchase #6	$215.79	11.556%	$240.7267	$240.73	$240.75	$240.70
Purchase #7	$146.59	3.208%	$151.2926	$151.29	$151.30	$151.30
7 purchase totals =	$836.85		$898.3824	$898.38	$898.40	$898.40