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	$156.89	9.802%	$172.2684	$172.27	$172.25	$172.30
Purchase #2	$98.92	3.571%	$102.4524	$102.45	$102.45	$102.50
Purchase #3	$114.83	10.155%	$126.491	$126.49	$126.50	$126.50
Purchase #4	$20.59	7.538%	$22.1421	$22.14	$22.15	$22.10
Purchase #5	$214.89	8.622%	$233.4178	$233.42	$233.40	$233.40
Purchase #6	$187.72	12.734%	$211.6243	$211.62	$211.60	$211.60
Purchase #7	$136.85	3.438%	$141.5549	$141.55	$141.55	$141.60
7 purchase totals =	$930.69		$1,009.9509	$1,009.94	$1,009.90	$1,010.00