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 $86.47   11.147%   $96.1088   $96.11   $96.10   $96.10  
  Purchase #2 $95.69   8.811%   $104.1212   $104.12   $104.10   $104.10  
  Purchase #3 $146.63   12.795%   $165.3913   $165.39   $165.40   $165.40  
  Purchase #4 $184.77   10.410%   $204.0046   $204.00   $204.00   $204.00  
  Purchase #5 $169.98   5.114%   $178.6728   $178.67   $178.65   $178.70  
  Purchase #6 $196.26   5.270%   $206.6029   $206.60   $206.60   $206.60  
  Purchase #7 $63.27   11.606%   $70.6131   $70.61   $70.60   $70.60  
  7 purchase totals = $943.07       $1,025.5147   $1,025.50   $1,025.45   $1,025.50