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	$127.34	3.249%	$131.4773	$131.48	$131.50	$131.50
Purchase #2	$85.76	5.312%	$90.3156	$90.32	$90.30	$90.30
Purchase #3	$63.72	7.431%	$68.455	$68.46	$68.45	$68.50
Purchase #4	$123.50	12.862%	$139.3846	$139.38	$139.40	$139.40
Purchase #5	$14.48	9.374%	$15.8374	$15.84	$15.85	$15.80
Purchase #6	$165.92	7.390%	$178.1815	$178.18	$178.20	$178.20
Purchase #7	$214.77	3.718%	$222.7551	$222.76	$222.75	$222.80
7 purchase totals =	$795.49		$846.4065	$846.42	$846.45	$846.50