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 $83.89   13.368%   $95.1044   $95.10   $95.10   $95.10  
  Purchase #2 $121.87   13.193%   $137.9483   $137.95   $137.95   $137.90  
  Purchase #3 $229.74   8.654%   $249.6217   $249.62   $249.60   $249.60  
  Purchase #4 $151.61   8.372%   $164.3028   $164.30   $164.30   $164.30  
  Purchase #5 $144.68   11.184%   $160.861   $160.86   $160.85   $160.90  
  Purchase #6 $106.65   6.175%   $113.2356   $113.24   $113.25   $113.20  
  Purchase #7 $212.68   10.605%   $235.2347   $235.23   $235.25   $235.20  
  7 purchase totals = $1,051.12       $1,156.3085   $1,156.30   $1,156.30   $1,156.20