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 $160.49   9.379%   $175.5424   $175.54   $175.55   $175.50  
  Purchase #2 $231.42   5.703%   $244.6179   $244.62   $244.60   $244.60  
  Purchase #3 $227.70   13.629%   $258.7332   $258.73   $258.75   $258.70  
  Purchase #4 $208.81   4.355%   $217.9037   $217.90   $217.90   $217.90  
  Purchase #5 $209.38   5.260%   $220.3934   $220.39   $220.40   $220.40  
  Purchase #6 $203.66   12.228%   $228.5635   $228.56   $228.55   $228.60  
  Purchase #7 $250.25   7.405%   $268.781   $268.78   $268.80   $268.80  
  7 purchase totals = $1,491.71       $1,614.5351   $1,614.52   $1,614.55   $1,614.50