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 $84.34   9.709%   $92.5286   $92.53   $92.55   $92.50  
  Purchase #2 $212.70   13.605%   $241.6378   $241.64   $241.65   $241.60  
  Purchase #3 $94.92   6.636%   $101.2189   $101.22   $101.20   $101.20  
  Purchase #4 $157.33   4.266%   $164.0417   $164.04   $164.05   $164.00  
  Purchase #5 $134.26   6.702%   $143.2581   $143.26   $143.25   $143.30  
  Purchase #6 $51.28   4.513%   $53.5943   $53.59   $53.60   $53.60  
  Purchase #7 $201.35   6.663%   $214.766   $214.77   $214.75   $214.80  
  7 purchase totals = $936.18       $1,011.0454   $1,011.05   $1,011.05   $1,011.00