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	$113.51	5.490%	$119.7417	$119.74	$119.75	$119.70
Purchase #2	$184.70	8.356%	$200.1335	$200.13	$200.15	$200.10
Purchase #3	$36.49	5.525%	$38.5061	$38.51	$38.50	$38.50
Purchase #4	$73.53	6.201%	$78.0896	$78.09	$78.10	$78.10
Purchase #5	$31.70	10.689%	$35.0884	$35.09	$35.10	$35.10
Purchase #6	$212.53	13.711%	$241.67	$241.67	$241.65	$241.70
Purchase #7	$143.42	8.456%	$155.5476	$155.55	$155.55	$155.50
7 purchase totals =	$795.88		$868.7769	$868.78	$868.80	$868.70