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	$81.75	4.430%	$85.3715	$85.37	$85.35	$85.40
Purchase #2	$143.46	6.595%	$152.9212	$152.92	$152.90	$152.90
Purchase #3	$237.39	3.870%	$246.577	$246.58	$246.60	$246.60
Purchase #4	$145.49	11.861%	$162.7466	$162.75	$162.75	$162.70
Purchase #5	$16.66	13.207%	$18.8603	$18.86	$18.85	$18.90
Purchase #6	$82.45	3.346%	$85.2088	$85.21	$85.20	$85.20
Purchase #7	$81.56	4.650%	$85.3525	$85.35	$85.35	$85.40
7 purchase totals =	$788.76		$837.0379	$837.04	$837.00	$837.10