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 $43.96   5.680%   $46.4569   $46.46   $46.45   $46.50  
  Purchase #2 $196.55   3.610%   $203.6455   $203.65   $203.65   $203.60  
  Purchase #3 $161.96   11.816%   $181.0972   $181.10   $181.10   $181.10  
  Purchase #4 $15.95   7.694%   $17.1772   $17.18   $17.20   $17.20  
  Purchase #5 $131.81   5.627%   $139.2269   $139.23   $139.25   $139.20  
  Purchase #6 $210.34   11.595%   $234.7289   $234.73   $234.75   $234.70  
  Purchase #7 $41.51   6.429%   $44.1787   $44.18   $44.20   $44.20  
  7 purchase totals = $802.08       $866.5113   $866.53   $866.60   $866.50