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	$176.34	13.471%	$200.0948	$200.09	$200.10	$200.10
Purchase #2	$39.78	9.532%	$43.5718	$43.57	$43.55	$43.60
Purchase #3	$22.93	9.410%	$25.0877	$25.09	$25.10	$25.10
Purchase #4	$131.89	10.245%	$145.4021	$145.40	$145.40	$145.40
Purchase #5	$96.48	4.557%	$100.8766	$100.88	$100.90	$100.90
Purchase #6	$153.48	5.233%	$161.5116	$161.51	$161.50	$161.50
Purchase #7	$104.29	6.634%	$111.2086	$111.21	$111.20	$111.20
7 purchase totals =	$725.19		$787.7532	$787.75	$787.75	$787.80