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 $43.35   6.691%   $46.2505   $46.25   $46.25   $46.30  
  Purchase #2 $93.75   11.866%   $104.8744   $104.87   $104.85   $104.90  
  Purchase #3 $245.61   12.765%   $276.9621   $276.96   $276.95   $277.00  
  Purchase #4 $126.81   13.857%   $144.3821   $144.38   $144.40   $144.40  
  Purchase #5 $146.36   5.614%   $154.5767   $154.58   $154.60   $154.60  
  Purchase #6 $157.61   11.592%   $175.8802   $175.88   $175.90   $175.90  
  Purchase #7 $209.68   10.582%   $231.8683   $231.87   $231.85   $231.90  
  7 purchase totals = $1,023.17       $1,134.7943   $1,134.79   $1,134.80   $1,135.00