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 $169.44   5.756%   $179.193   $179.19   $179.20   $179.20  
  Purchase #2 $211.83   10.685%   $234.464   $234.46   $234.45   $234.50  
  Purchase #3 $93.30   5.715%   $98.6321   $98.63   $98.65   $98.60  
  Purchase #4 $172.57   9.302%   $188.6225   $188.62   $188.60   $188.60  
  Purchase #5 $225.46   9.462%   $246.793   $246.79   $246.80   $246.80  
  Purchase #6 $201.73   9.380%   $220.6523   $220.65   $220.65   $220.70  
  Purchase #7 $26.49   5.661%   $27.9896   $27.99   $28.00   $28.00  
  7 purchase totals = $1,100.82       $1,196.3465   $1,196.33   $1,196.35   $1,196.40