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	$108.93	3.322%	$112.5487	$112.55	$112.55	$112.50
Purchase #2	$141.32	6.321%	$150.2528	$150.25	$150.25	$150.30
Purchase #3	$158.36	6.513%	$168.674	$168.67	$168.65	$168.70
Purchase #4	$172.63	11.471%	$192.4324	$192.43	$192.45	$192.40
Purchase #5	$153.59	4.535%	$160.5553	$160.56	$160.55	$160.60
Purchase #6	$138.31	3.491%	$143.1384	$143.14	$143.15	$143.10
Purchase #7	$57.50	9.850%	$63.1638	$63.16	$63.15	$63.20
7 purchase totals =	$930.64		$990.7654	$990.76	$990.75	$990.80