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 $176.86   10.619%   $195.6408   $195.64   $195.65   $195.60  
  Purchase #2 $83.28   13.684%   $94.676   $94.68   $94.70   $94.70  
  Purchase #3 $64.43   4.207%   $67.1406   $67.14   $67.15   $67.10  
  Purchase #4 $208.80   5.611%   $220.5158   $220.52   $220.50   $220.50  
  Purchase #5 $38.92   4.743%   $40.766   $40.77   $40.75   $40.80  
  Purchase #6 $131.93   10.818%   $146.2022   $146.20   $146.20   $146.20  
  Purchase #7 $72.56   13.303%   $82.2127   $82.21   $82.20   $82.20  
  7 purchase totals = $776.78       $847.1541   $847.16   $847.15   $847.10