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 $58.93   6.367%   $62.6821   $62.68   $62.70   $62.70  
  Purchase #2 $195.50   10.338%   $215.7108   $215.71   $215.70   $215.70  
  Purchase #3 $91.81   4.259%   $95.7202   $95.72   $95.70   $95.70  
  Purchase #4 $237.54   4.365%   $247.9086   $247.91   $247.90   $247.90  
  Purchase #5 $192.56   7.642%   $207.2754   $207.28   $207.30   $207.30  
  Purchase #6 $234.28   4.238%   $244.2088   $244.21   $244.20   $244.20  
  Purchase #7 $80.82   6.665%   $86.2067   $86.21   $86.20   $86.20  
  7 purchase totals = $1,091.44       $1,159.7126   $1,159.72   $1,159.70   $1,159.70