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 $244.56   8.337%   $264.949   $264.95   $264.95   $264.90  
  Purchase #2 $70.77   12.237%   $79.4301   $79.43   $79.45   $79.40  
  Purchase #3 $174.36   8.103%   $188.4884   $188.49   $188.50   $188.50  
  Purchase #4 $176.44   12.102%   $197.7928   $197.79   $197.80   $197.80  
  Purchase #5 $165.63   5.187%   $174.2212   $174.22   $174.20   $174.20  
  Purchase #6 $114.50   5.420%   $120.7059   $120.71   $120.70   $120.70  
  Purchase #7 $148.97   7.156%   $159.6303   $159.63   $159.65   $159.60  
  7 purchase totals = $1,095.23       $1,185.2177   $1,185.22   $1,185.25   $1,185.10