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 $168.26   11.567%   $187.7226   $187.72   $187.70   $187.70  
  Purchase #2 $71.56   6.235%   $76.0218   $76.02   $76.00   $76.00  
  Purchase #3 $14.80   7.761%   $15.9486   $15.95   $15.95   $15.90  
  Purchase #4 $116.58   5.709%   $123.2356   $123.24   $123.25   $123.20  
  Purchase #5 $225.53   3.265%   $232.8936   $232.89   $232.90   $232.90  
  Purchase #6 $207.69   11.393%   $231.3521   $231.35   $231.35   $231.40  
  Purchase #7 $135.25   10.285%   $149.1605   $149.16   $149.15   $149.20  
  7 purchase totals = $939.67       $1,016.3348   $1,016.33   $1,016.30   $1,016.30