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 $205.26   10.411%   $226.6296   $226.63   $226.65   $226.60  
  Purchase #2 $164.87   12.208%   $184.9973   $185.00   $185.00   $185.00  
  Purchase #3 $54.74   6.378%   $58.2313   $58.23   $58.25   $58.20  
  Purchase #4 $88.98   11.150%   $98.9013   $98.90   $98.90   $98.90  
  Purchase #5 $93.55   5.216%   $98.4296   $98.43   $98.45   $98.40  
  Purchase #6 $234.51   7.362%   $251.7746   $251.77   $251.75   $251.80  
  Purchase #7 $137.39   8.423%   $148.9624   $148.96   $148.95   $149.00  
  7 purchase totals = $979.30       $1,067.9261   $1,067.92   $1,067.95   $1,067.90