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	$24.59	5.526%	$25.9488	$25.95	$25.95	$25.90
Purchase #2	$118.49	11.446%	$132.0524	$132.05	$132.05	$132.10
Purchase #3	$200.54	11.822%	$224.2478	$224.25	$224.25	$224.20
Purchase #4	$6.72	11.282%	$7.4782	$7.48	$7.50	$7.50
Purchase #5	$126.89	11.609%	$141.6207	$141.62	$141.60	$141.60
Purchase #6	$91.97	7.402%	$98.7776	$98.78	$98.80	$98.80
Purchase #7	$198.90	10.154%	$219.0963	$219.10	$219.10	$219.10
7 purchase totals =	$768.10		$849.2218	$849.23	$849.25	$849.20