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	$212.45	13.307%	$240.7207	$240.72	$240.70	$240.70
Purchase #2	$47.60	5.317%	$50.1309	$50.13	$50.15	$50.10
Purchase #3	$227.99	11.587%	$254.4072	$254.41	$254.40	$254.40
Purchase #4	$83.37	6.613%	$88.8833	$88.88	$88.90	$88.90
Purchase #5	$238.25	13.256%	$269.8324	$269.83	$269.85	$269.80
Purchase #6	$238.33	7.784%	$256.8816	$256.88	$256.90	$256.90
Purchase #7	$5.42	12.602%	$6.103	$6.10	$6.10	$6.10
7 purchase totals =	$1,053.41		$1,166.9591	$1,166.95	$1,167.00	$1,166.90