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 $46.95   12.165%   $52.6615   $52.66   $52.65   $52.70  
  Purchase #2 $233.97   7.568%   $251.6768   $251.68   $251.70   $251.70  
  Purchase #3 $71.46   12.583%   $80.4518   $80.45   $80.45   $80.50  
  Purchase #4 $122.98   3.160%   $126.8662   $126.87   $126.85   $126.90  
  Purchase #5 $59.81   13.179%   $67.6924   $67.69   $67.70   $67.70  
  Purchase #6 $152.63   12.761%   $172.1071   $172.11   $172.10   $172.10  
  Purchase #7 $186.41   7.233%   $199.893   $199.89   $199.90   $199.90  
  7 purchase totals = $874.21       $951.3488   $951.35   $951.35   $951.50