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 $213.95   10.131%   $235.6253   $235.63   $235.65   $235.60  
  Purchase #2 $71.47   6.138%   $75.8568   $75.86   $75.85   $75.90  
  Purchase #3 $156.57   10.660%   $173.2604   $173.26   $173.25   $173.30  
  Purchase #4 $171.64   8.775%   $186.7014   $186.70   $186.70   $186.70  
  Purchase #5 $191.31   6.654%   $204.0398   $204.04   $204.05   $204.00  
  Purchase #6 $193.45   4.371%   $201.9057   $201.91   $201.90   $201.90  
  Purchase #7 $178.84   11.538%   $199.4746   $199.47   $199.45   $199.50  
  7 purchase totals = $1,177.23       $1,276.8640   $1,276.87   $1,276.85   $1,276.90