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 $125.45   5.462%   $132.3021   $132.30   $132.30   $132.30  
  Purchase #2 $156.76   5.525%   $165.421   $165.42   $165.40   $165.40  
  Purchase #3 $206.90   5.382%   $218.0354   $218.04   $218.05   $218.00  
  Purchase #4 $234.27   11.621%   $261.4945   $261.49   $261.50   $261.50  
  Purchase #5 $243.77   13.852%   $277.537   $277.54   $277.55   $277.50  
  Purchase #6 $17.75   11.599%   $19.8088   $19.81   $19.80   $19.80  
  Purchase #7 $210.53   6.357%   $223.9134   $223.91   $223.90   $223.90  
  7 purchase totals = $1,195.43       $1,298.5122   $1,298.51   $1,298.50   $1,298.40