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	$206.40	9.695%	$226.4105	$226.41	$226.40	$226.40
Purchase #2	$213.62	11.755%	$238.731	$238.73	$238.75	$238.70
Purchase #3	$82.63	3.416%	$85.4526	$85.45	$85.45	$85.50
Purchase #4	$35.33	6.626%	$37.671	$37.67	$37.65	$37.70
Purchase #5	$6.25	4.317%	$6.5198	$6.52	$6.50	$6.50
Purchase #6	$238.40	6.765%	$254.5278	$254.53	$254.55	$254.50
Purchase #7	$176.61	7.675%	$190.1648	$190.16	$190.15	$190.20
7 purchase totals =	$959.24		$1,039.4775	$1,039.47	$1,039.45	$1,039.50