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	$72.49	5.408%	$76.4103	$76.41	$76.40	$76.40
Purchase #2	$11.96	12.590%	$13.4658	$13.47	$13.45	$13.50
Purchase #3	$210.78	12.475%	$237.0748	$237.07	$237.05	$237.10
Purchase #4	$158.25	9.210%	$172.8248	$172.82	$172.80	$172.80
Purchase #5	$222.35	8.169%	$240.5138	$240.51	$240.50	$240.50
Purchase #6	$173.57	8.712%	$188.6914	$188.69	$188.70	$188.70
Purchase #7	$129.49	11.102%	$143.866	$143.87	$143.85	$143.90
7 purchase totals =	$978.89		$1,072.8469	$1,072.84	$1,072.75	$1,072.90