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 $196.76   4.175%   $204.9747   $204.97   $204.95   $205.00  
  Purchase #2 $188.69   4.703%   $197.5641   $197.56   $197.55   $197.60  
  Purchase #3 $54.47   8.599%   $59.1539   $59.15   $59.15   $59.20  
  Purchase #4 $186.31   9.622%   $204.2367   $204.24   $204.25   $204.20  
  Purchase #5 $108.73   10.278%   $119.9053   $119.91   $119.90   $119.90  
  Purchase #6 $181.90   3.147%   $187.6244   $187.62   $187.60   $187.60  
  Purchase #7 $212.49   8.777%   $231.1402   $231.14   $231.15   $231.10  
  7 purchase totals = $1,129.35       $1,204.5993   $1,204.59   $1,204.55   $1,204.60