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 $172.69   13.261%   $195.5904   $195.59   $195.60   $195.60  
  Purchase #2 $44.57   4.542%   $46.5944   $46.59   $46.60   $46.60  
  Purchase #3 $137.38   8.732%   $149.376   $149.38   $149.40   $149.40  
  Purchase #4 $228.51   6.693%   $243.8042   $243.80   $243.80   $243.80  
  Purchase #5 $54.88   12.439%   $61.7065   $61.71   $61.70   $61.70  
  Purchase #6 $125.71   6.312%   $133.6448   $133.64   $133.65   $133.60  
  Purchase #7 $50.29   7.119%   $53.8701   $53.87   $53.85   $53.90  
  7 purchase totals = $814.03       $884.5864   $884.58   $884.60   $884.60