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	$59.41	6.113%	$63.0417	$63.04	$63.05	$63.00
Purchase #2	$40.85	11.476%	$45.5379	$45.54	$45.55	$45.50
Purchase #3	$92.29	12.264%	$103.6084	$103.61	$103.60	$103.60
Purchase #4	$167.46	6.416%	$178.2042	$178.20	$178.20	$178.20
Purchase #5	$190.32	10.627%	$210.5453	$210.55	$210.55	$210.50
Purchase #6	$147.56	5.741%	$156.0314	$156.03	$156.05	$156.00
Purchase #7	$181.92	13.745%	$206.9249	$206.92	$206.90	$206.90
7 purchase totals =	$879.81		$963.8938	$963.89	$963.90	$963.70