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	$161.66	6.201%	$171.6845	$171.68	$171.70	$171.70
Purchase #2	$40.94	9.165%	$44.6922	$44.69	$44.70	$44.70
Purchase #3	$174.31	9.454%	$190.7893	$190.79	$190.80	$190.80
Purchase #4	$237.30	7.597%	$255.3277	$255.33	$255.35	$255.30
Purchase #5	$174.57	7.381%	$187.455	$187.46	$187.45	$187.50
Purchase #6	$5.95	7.238%	$6.3807	$6.38	$6.40	$6.40
Purchase #7	$158.39	8.776%	$172.2903	$172.29	$172.30	$172.30
7 purchase totals =	$953.12		$1,028.6197	$1,028.62	$1,028.70	$1,028.70