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 $197.44   13.458%   $224.0115   $224.01   $224.00   $224.00  
  Purchase #2 $220.38   7.296%   $236.4589   $236.46   $236.45   $236.50  
  Purchase #3 $63.97   6.625%   $68.208   $68.21   $68.20   $68.20  
  Purchase #4 $192.44   4.702%   $201.4885   $201.49   $201.50   $201.50  
  Purchase #5 $23.32   12.237%   $26.1737   $26.17   $26.15   $26.20  
  Purchase #6 $218.26   6.597%   $232.6586   $232.66   $232.65   $232.70  
  Purchase #7 $211.53   3.238%   $218.3793   $218.38   $218.40   $218.40  
  7 purchase totals = $1,127.34       $1,207.3785   $1,207.38   $1,207.35   $1,207.50