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 $58.69   3.481%   $60.733   $60.73   $60.75   $60.70  
  Purchase #2 $232.27   12.663%   $261.6824   $261.68   $261.70   $261.70  
  Purchase #3 $57.71   7.318%   $61.9332   $61.93   $61.95   $61.90  
  Purchase #4 $210.30   9.167%   $229.5782   $229.58   $229.60   $229.60  
  Purchase #5 $11.97   9.599%   $13.119   $13.12   $13.10   $13.10  
  Purchase #6 $133.37   10.726%   $147.6753   $147.68   $147.70   $147.70  
  Purchase #7 $190.57   10.233%   $210.071   $210.07   $210.05   $210.10  
  7 purchase totals = $894.88       $984.7921   $984.79   $984.85   $984.80