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 $45.47   3.544%   $47.0815   $47.08   $47.10   $47.10  
  Purchase #2 $212.57   13.226%   $240.6845   $240.68   $240.70   $240.70  
  Purchase #3 $55.64   5.346%   $58.6145   $58.61   $58.60   $58.60  
  Purchase #4 $132.66   10.500%   $146.5893   $146.59   $146.60   $146.60  
  Purchase #5 $203.98   6.233%   $216.6941   $216.69   $216.70   $216.70  
  Purchase #6 $230.85   13.115%   $261.126   $261.13   $261.15   $261.10  
  Purchase #7 $244.39   11.323%   $272.0623   $272.06   $272.05   $272.10  
  7 purchase totals = $1,125.56       $1,242.8522   $1,242.84   $1,242.90   $1,242.90