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	$57.60	5.779%	$60.9287	$60.93	$60.95	$60.90
Purchase #2	$52.90	13.116%	$59.8384	$59.84	$59.85	$59.80
Purchase #3	$228.80	4.402%	$238.8718	$238.87	$238.85	$238.90
Purchase #4	$180.30	4.153%	$187.7879	$187.79	$187.80	$187.80
Purchase #5	$217.60	5.648%	$229.89	$229.89	$229.90	$229.90
Purchase #6	$156.92	8.315%	$169.9679	$169.97	$169.95	$170.00
Purchase #7	$163.48	6.179%	$173.5814	$173.58	$173.60	$173.60
7 purchase totals =	$1,057.60		$1,120.8661	$1,120.87	$1,120.90	$1,120.90