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	$57.47	12.333%	$64.5578	$64.56	$64.55	$64.60
Purchase #2	$65.92	10.683%	$72.9622	$72.96	$72.95	$73.00
Purchase #3	$89.33	3.342%	$92.3154	$92.32	$92.30	$92.30
Purchase #4	$164.72	11.652%	$183.9132	$183.91	$183.90	$183.90
Purchase #5	$172.59	4.102%	$179.6696	$179.67	$179.65	$179.70
Purchase #6	$133.54	4.750%	$139.8832	$139.88	$139.90	$139.90
Purchase #7	$220.35	5.862%	$233.2669	$233.27	$233.25	$233.30
7 purchase totals =	$903.92		$966.5683	$966.57	$966.50	$966.70