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 $98.81   6.781%   $105.5103   $105.51   $105.50   $105.50  
  Purchase #2 $246.59   8.288%   $267.0274   $267.03   $267.05   $267.00  
  Purchase #3 $249.61   3.458%   $258.2415   $258.24   $258.25   $258.20  
  Purchase #4 $60.92   8.661%   $66.1963   $66.20   $66.20   $66.20  
  Purchase #5 $238.47   6.599%   $254.2066   $254.21   $254.20   $254.20  
  Purchase #6 $233.58   13.474%   $265.0526   $265.05   $265.05   $265.10  
  Purchase #7 $215.82   5.351%   $227.3685   $227.37   $227.35   $227.40  
  7 purchase totals = $1,343.80       $1,443.6032   $1,443.61   $1,443.60   $1,443.60