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	$196.91	5.720%	$208.1733	$208.17	$208.15	$208.20
Purchase #2	$43.43	11.735%	$48.5265	$48.53	$48.55	$48.50
Purchase #3	$40.31	5.369%	$42.4742	$42.47	$42.45	$42.50
Purchase #4	$177.87	6.650%	$189.6984	$189.70	$189.70	$189.70
Purchase #5	$58.59	3.429%	$60.5991	$60.60	$60.60	$60.60
Purchase #6	$192.66	5.123%	$202.53	$202.53	$202.55	$202.50
Purchase #7	$77.72	5.645%	$82.1073	$82.11	$82.10	$82.10
7 purchase totals =	$787.49		$834.1088	$834.11	$834.10	$834.10