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 $190.86   5.660%   $201.6627   $201.66   $201.65   $201.70  
  Purchase #2 $218.70   5.719%   $231.2075   $231.21   $231.20   $231.20  
  Purchase #3 $79.38   4.353%   $82.8354   $82.84   $82.85   $82.80  
  Purchase #4 $157.83   11.729%   $176.3419   $176.34   $176.35   $176.30  
  Purchase #5 $17.33   7.713%   $18.6667   $18.67   $18.65   $18.70  
  Purchase #6 $191.41   12.346%   $215.0415   $215.04   $215.05   $215.00  
  Purchase #7 $66.65   12.610%   $75.0546   $75.05   $75.05   $75.10  
  7 purchase totals = $922.16       $1,000.8103   $1,000.81   $1,000.80   $1,000.80