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 $238.58   9.438%   $261.0972   $261.10   $261.10   $261.10  
  Purchase #2 $28.57   13.417%   $32.4032   $32.40   $32.40   $32.40  
  Purchase #3 $160.79   4.699%   $168.3455   $168.35   $168.35   $168.30  
  Purchase #4 $141.91   12.566%   $159.7424   $159.74   $159.75   $159.70  
  Purchase #5 $121.59   3.327%   $125.6353   $125.64   $125.65   $125.60  
  Purchase #6 $40.87   8.343%   $44.2798   $44.28   $44.30   $44.30  
  Purchase #7 $244.80   4.860%   $256.6973   $256.70   $256.70   $256.70  
  7 purchase totals = $977.11       $1,048.2007   $1,048.21   $1,048.25   $1,048.10