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 $174.96   11.550%   $195.1679   $195.17   $195.15   $195.20  
  Purchase #2 $250.44   4.387%   $261.4268   $261.43   $261.45   $261.40  
  Purchase #3 $230.76   4.258%   $240.5858   $240.59   $240.60   $240.60  
  Purchase #4 $148.76   3.220%   $153.5501   $153.55   $153.55   $153.60  
  Purchase #5 $229.49   13.594%   $260.6869   $260.69   $260.70   $260.70  
  Purchase #6 $8.82   4.212%   $9.1915   $9.19   $9.20   $9.20  
  Purchase #7 $223.29   10.495%   $246.7243   $246.72   $246.70   $246.70  
  7 purchase totals = $1,266.52       $1,367.3333   $1,367.34   $1,367.35   $1,367.40