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 $212.62   11.417%   $236.8948   $236.89   $236.90   $236.90  
  Purchase #2 $168.32   12.724%   $189.737   $189.74   $189.75   $189.70  
  Purchase #3 $68.39   12.809%   $77.1501   $77.15   $77.15   $77.20  
  Purchase #4 $65.80   5.385%   $69.3433   $69.34   $69.35   $69.30  
  Purchase #5 $103.74   10.421%   $114.5507   $114.55   $114.55   $114.60  
  Purchase #6 $128.82   5.235%   $135.5637   $135.56   $135.55   $135.60  
  Purchase #7 $188.77   7.673%   $203.2543   $203.25   $203.25   $203.30  
  7 purchase totals = $936.46       $1,026.4939   $1,026.48   $1,026.50   $1,026.60