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	$214.56	12.179%	$240.6913	$240.69	$240.70	$240.70
Purchase #2	$65.45	6.520%	$69.7173	$69.72	$69.70	$69.70
Purchase #3	$44.77	7.670%	$48.2039	$48.20	$48.20	$48.20
Purchase #4	$145.82	12.497%	$164.0431	$164.04	$164.05	$164.00
Purchase #5	$82.95	3.548%	$85.8931	$85.89	$85.90	$85.90
Purchase #6	$157.30	7.360%	$168.8773	$168.88	$168.90	$168.90
Purchase #7	$80.74	12.449%	$90.7913	$90.79	$90.80	$90.80
7 purchase totals =	$791.59		$868.2173	$868.21	$868.25	$868.20