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	$237.54	7.759%	$255.9707	$255.97	$255.95	$256.00
Purchase #2	$132.67	10.354%	$146.4067	$146.41	$146.40	$146.40
Purchase #3	$121.37	8.281%	$131.4206	$131.42	$131.40	$131.40
Purchase #4	$187.88	13.749%	$213.7116	$213.71	$213.70	$213.70
Purchase #5	$62.81	13.268%	$71.1436	$71.14	$71.15	$71.10
Purchase #6	$40.28	5.122%	$42.3431	$42.34	$42.35	$42.30
Purchase #7	$176.28	6.397%	$187.5566	$187.56	$187.55	$187.60
7 purchase totals =	$958.83		$1,048.5529	$1,048.55	$1,048.50	$1,048.50