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 $186.63   7.704%   $201.008   $201.01   $201.00   $201.00  
  Purchase #2 $94.84   8.574%   $102.9716   $102.97   $102.95   $103.00  
  Purchase #3 $135.49   6.188%   $143.8741   $143.87   $143.85   $143.90  
  Purchase #4 $222.67   7.150%   $238.5909   $238.59   $238.60   $238.60  
  Purchase #5 $93.60   8.681%   $101.7254   $101.73   $101.75   $101.70  
  Purchase #6 $170.62   7.552%   $183.5052   $183.51   $183.50   $183.50  
  Purchase #7 $124.59   4.733%   $130.4868   $130.49   $130.50   $130.50  
  7 purchase totals = $1,028.44       $1,102.1620   $1,102.17   $1,102.15   $1,102.20