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 $58.46   9.197%   $63.8366   $63.84   $63.85   $63.80  
  Purchase #2 $132.38   9.310%   $144.7046   $144.70   $144.70   $144.70  
  Purchase #3 $15.47   5.594%   $16.3354   $16.34   $16.35   $16.30  
  Purchase #4 $208.72   3.279%   $215.5639   $215.56   $215.55   $215.60  
  Purchase #5 $46.31   11.482%   $51.6273   $51.63   $51.65   $51.60  
  Purchase #6 $166.54   10.371%   $183.8119   $183.81   $183.80   $183.80  
  Purchase #7 $102.73   3.169%   $105.9855   $105.99   $106.00   $106.00  
  7 purchase totals = $730.61       $781.8652   $781.87   $781.90   $781.80