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 $52.60   3.462%   $54.421   $54.42   $54.40   $54.40  
  Purchase #2 $235.44   12.113%   $263.9588   $263.96   $263.95   $264.00  
  Purchase #3 $54.70   3.676%   $56.7108   $56.71   $56.70   $56.70  
  Purchase #4 $206.93   9.504%   $226.5966   $226.60   $226.60   $226.60  
  Purchase #5 $153.81   8.611%   $167.0546   $167.05   $167.05   $167.10  
  Purchase #6 $179.25   7.472%   $192.6436   $192.64   $192.65   $192.60  
  Purchase #7 $76.63   10.495%   $84.6723   $84.67   $84.65   $84.70  
  7 purchase totals = $959.36       $1,046.0577   $1,046.05   $1,046.00   $1,046.10