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	$140.43	11.863%	$157.0892	$157.09	$157.10	$157.10
Purchase #2	$142.85	11.322%	$159.0235	$159.02	$159.00	$159.00
Purchase #3	$125.71	9.397%	$137.523	$137.52	$137.50	$137.50
Purchase #4	$32.31	10.703%	$35.7681	$35.77	$35.75	$35.80
Purchase #5	$174.93	5.417%	$184.406	$184.41	$184.40	$184.40
Purchase #6	$159.89	12.255%	$179.4845	$179.48	$179.50	$179.50
Purchase #7	$139.25	11.751%	$155.6133	$155.61	$155.60	$155.60
7 purchase totals =	$915.37		$1,008.9076	$1,008.90	$1,008.85	$1,008.90