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	$13.27	3.606%	$13.7485	$13.75	$13.75	$13.70
Purchase #2	$168.45	7.114%	$180.4335	$180.43	$180.45	$180.40
Purchase #3	$76.89	12.713%	$86.665	$86.67	$86.65	$86.70
Purchase #4	$152.53	12.822%	$172.0874	$172.09	$172.10	$172.10
Purchase #5	$247.65	6.168%	$262.9251	$262.93	$262.95	$262.90
Purchase #6	$139.66	8.213%	$151.1303	$151.13	$151.15	$151.10
Purchase #7	$94.88	5.585%	$100.179	$100.18	$100.20	$100.20
7 purchase totals =	$893.33		$967.1688	$967.18	$967.25	$967.10