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 $72.54   5.752%   $76.7125   $76.71   $76.70   $76.70  
  Purchase #2 $113.80   10.822%   $126.1154   $126.12   $126.10   $126.10  
  Purchase #3 $97.75   10.821%   $108.3275   $108.33   $108.35   $108.30  
  Purchase #4 $51.80   10.485%   $57.2312   $57.23   $57.25   $57.20  
  Purchase #5 $164.91   11.349%   $183.6256   $183.63   $183.65   $183.60  
  Purchase #6 $52.39   9.386%   $57.3073   $57.31   $57.30   $57.30  
  Purchase #7 $95.46   7.438%   $102.5603   $102.56   $102.55   $102.60  
  7 purchase totals = $648.65       $711.8798   $711.89   $711.90   $711.80