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	$136.29	3.692%	$141.3218	$141.32	$141.30	$141.30
Purchase #2	$131.45	4.762%	$137.7096	$137.71	$137.70	$137.70
Purchase #3	$213.71	6.851%	$228.3513	$228.35	$228.35	$228.40
Purchase #4	$73.35	7.557%	$78.8931	$78.89	$78.90	$78.90
Purchase #5	$79.66	3.776%	$82.668	$82.67	$82.65	$82.70
Purchase #6	$224.81	13.699%	$255.6067	$255.61	$255.60	$255.60
Purchase #7	$118.70	3.446%	$122.7904	$122.79	$122.80	$122.80
7 purchase totals =	$977.97		$1,047.3409	$1,047.34	$1,047.30	$1,047.40