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 $164.46   6.874%   $175.765   $175.77   $175.75   $175.80  
  Purchase #2 $170.91   3.514%   $176.9158   $176.92   $176.90   $176.90  
  Purchase #3 $171.56   9.578%   $187.992   $187.99   $188.00   $188.00  
  Purchase #4 $98.97   3.798%   $102.7289   $102.73   $102.75   $102.70  
  Purchase #5 $95.31   4.772%   $99.8582   $99.86   $99.85   $99.90  
  Purchase #6 $179.97   13.136%   $203.6109   $203.61   $203.60   $203.60  
  Purchase #7 $195.42   4.235%   $203.696   $203.70   $203.70   $203.70  
  7 purchase totals = $1,076.60       $1,150.5668   $1,150.58   $1,150.55   $1,150.60