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	$140.98	9.553%	$154.4478	$154.45	$154.45	$154.40
Purchase #2	$131.67	4.507%	$137.6044	$137.60	$137.60	$137.60
Purchase #3	$153.86	11.858%	$172.1047	$172.10	$172.10	$172.10
Purchase #4	$239.39	4.474%	$250.1003	$250.10	$250.10	$250.10
Purchase #5	$172.62	11.750%	$192.9029	$192.90	$192.90	$192.90
Purchase #6	$213.47	4.476%	$223.0249	$223.02	$223.00	$223.00
Purchase #7	$211.36	6.643%	$225.4006	$225.40	$225.40	$225.40
7 purchase totals =	$1,263.35		$1,355.5856	$1,355.57	$1,355.55	$1,355.50