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 $227.32   9.841%   $249.6906   $249.69   $249.70   $249.70  
  Purchase #2 $146.78   3.393%   $151.7602   $151.76   $151.75   $151.80  
  Purchase #3 $86.55   10.831%   $95.9242   $95.92   $95.90   $95.90  
  Purchase #4 $228.89   7.846%   $246.8487   $246.85   $246.85   $246.80  
  Purchase #5 $140.63   11.328%   $156.5606   $156.56   $156.55   $156.60  
  Purchase #6 $116.35   4.699%   $121.8173   $121.82   $121.80   $121.80  
  Purchase #7 $72.74   11.866%   $81.3713   $81.37   $81.35   $81.40  
  7 purchase totals = $1,019.26       $1,103.9729   $1,103.97   $1,103.90   $1,104.00