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	$128.25	10.497%	$141.7124	$141.71	$141.70	$141.70
Purchase #2	$23.88	13.735%	$27.1599	$27.16	$27.15	$27.20
Purchase #3	$139.81	9.329%	$152.8529	$152.85	$152.85	$152.90
Purchase #4	$199.71	4.321%	$208.3395	$208.34	$208.35	$208.30
Purchase #5	$236.25	3.745%	$245.0976	$245.10	$245.10	$245.10
Purchase #6	$88.98	10.814%	$98.6023	$98.60	$98.60	$98.60
Purchase #7	$200.37	6.496%	$213.386	$213.39	$213.40	$213.40
7 purchase totals =	$1,017.25		$1,087.1506	$1,087.15	$1,087.15	$1,087.20