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 $232.26   5.389%   $244.7765   $244.78   $244.80   $244.80  
  Purchase #2 $155.55   13.288%   $176.2195   $176.22   $176.20   $176.20  
  Purchase #3 $227.54   8.419%   $246.6966   $246.70   $246.70   $246.70  
  Purchase #4 $52.88   6.725%   $56.4362   $56.44   $56.45   $56.40  
  Purchase #5 $218.92   9.706%   $240.1684   $240.17   $240.15   $240.20  
  Purchase #6 $247.47   8.347%   $268.1263   $268.13   $268.15   $268.10  
  Purchase #7 $162.82   6.119%   $172.783   $172.78   $172.80   $172.80  
  7 purchase totals = $1,297.44       $1,405.2065   $1,405.22   $1,405.25   $1,405.20