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	$69.89	12.435%	$78.5808	$78.58	$78.60	$78.60
Purchase #2	$175.25	12.379%	$196.9442	$196.94	$196.95	$196.90
Purchase #3	$213.72	4.188%	$222.6706	$222.67	$222.65	$222.70
Purchase #4	$6.48	10.742%	$7.1761	$7.18	$7.20	$7.20
Purchase #5	$68.82	5.112%	$72.3381	$72.34	$72.35	$72.30
Purchase #6	$136.97	9.486%	$149.963	$149.96	$149.95	$150.00
Purchase #7	$241.43	11.369%	$268.8782	$268.88	$268.90	$268.90
7 purchase totals =	$912.56		$996.5510	$996.55	$996.60	$996.60