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 $97.33   10.292%   $107.3472   $107.35   $107.35   $107.30  
  Purchase #2 $178.76   11.722%   $199.7142   $199.71   $199.70   $199.70  
  Purchase #3 $170.46   3.845%   $177.0142   $177.01   $177.00   $177.00  
  Purchase #4 $113.38   12.206%   $127.2192   $127.22   $127.20   $127.20  
  Purchase #5 $160.38   7.636%   $172.6266   $172.63   $172.65   $172.60  
  Purchase #6 $17.67   10.373%   $19.5029   $19.50   $19.50   $19.50  
  Purchase #7 $205.57   8.404%   $222.8461   $222.85   $222.85   $222.80  
  7 purchase totals = $943.55       $1,026.2704   $1,026.27   $1,026.25   $1,026.10