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 $55.38   6.498%   $58.9786   $58.98   $59.00   $59.00  
  Purchase #2 $176.28   13.165%   $199.4873   $199.49   $199.50   $199.50  
  Purchase #3 $242.85   6.238%   $257.999   $258.00   $258.00   $258.00  
  Purchase #4 $122.95   4.132%   $128.0303   $128.03   $128.05   $128.00  
  Purchase #5 $163.85   5.500%   $172.8618   $172.86   $172.85   $172.90  
  Purchase #6 $108.38   5.795%   $114.6606   $114.66   $114.65   $114.70  
  Purchase #7 $182.35   10.834%   $202.1058   $202.11   $202.10   $202.10  
  7 purchase totals = $1,052.04       $1,134.1234   $1,134.13   $1,134.15   $1,134.20