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 $73.29   3.670%   $75.9797   $75.98   $76.00   $76.00  
  Purchase #2 $177.41   5.207%   $186.6477   $186.65   $186.65   $186.60  
  Purchase #3 $173.80   5.540%   $183.4285   $183.43   $183.45   $183.40  
  Purchase #4 $228.39   12.637%   $257.2516   $257.25   $257.25   $257.30  
  Purchase #5 $188.55   6.709%   $201.1998   $201.20   $201.20   $201.20  
  Purchase #6 $23.63   9.409%   $25.8533   $25.85   $25.85   $25.90  
  Purchase #7 $242.99   8.111%   $262.6989   $262.70   $262.70   $262.70  
  7 purchase totals = $1,108.06       $1,193.0595   $1,193.06   $1,193.10   $1,193.10