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 $46.81   3.741%   $48.5612   $48.56   $48.55   $48.60  
  Purchase #2 $119.85   9.490%   $131.2238   $131.22   $131.20   $131.20  
  Purchase #3 $179.54   10.635%   $198.6341   $198.63   $198.65   $198.60  
  Purchase #4 $234.78   11.677%   $262.1953   $262.20   $262.20   $262.20  
  Purchase #5 $167.79   8.411%   $181.9028   $181.90   $181.90   $181.90  
  Purchase #6 $230.85   5.422%   $243.3667   $243.37   $243.35   $243.40  
  Purchase #7 $135.83   6.462%   $144.6073   $144.61   $144.60   $144.60  
  7 purchase totals = $1,115.45       $1,210.4912   $1,210.49   $1,210.45   $1,210.50