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 $87.38   8.749%   $95.0249   $95.02   $95.00   $95.00  
  Purchase #2 $225.69   12.357%   $253.5785   $253.58   $253.60   $253.60  
  Purchase #3 $77.93   6.665%   $83.124   $83.12   $83.10   $83.10  
  Purchase #4 $208.43   11.612%   $232.6329   $232.63   $232.65   $232.60  
  Purchase #5 $234.58   10.187%   $258.4767   $258.48   $258.50   $258.50  
  Purchase #6 $216.40   6.702%   $230.9031   $230.90   $230.90   $230.90  
  Purchase #7 $84.97   13.387%   $96.3449   $96.34   $96.35   $96.30  
  7 purchase totals = $1,135.38       $1,250.0850   $1,250.07   $1,250.10   $1,250.00