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	$124.70	7.669%	$134.2632	$134.26	$134.25	$134.30
Purchase #2	$182.87	5.248%	$192.467	$192.47	$192.45	$192.50
Purchase #3	$183.67	6.792%	$196.1449	$196.14	$196.15	$196.10
Purchase #4	$234.57	11.606%	$261.7942	$261.79	$261.80	$261.80
Purchase #5	$248.25	7.284%	$266.3325	$266.33	$266.35	$266.30
Purchase #6	$82.83	6.570%	$88.2719	$88.27	$88.25	$88.30
Purchase #7	$73.67	6.570%	$78.5101	$78.51	$78.50	$78.50
7 purchase totals =	$1,130.56		$1,217.7838	$1,217.77	$1,217.75	$1,217.80