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 $148.69   10.657%   $164.5359   $164.54   $164.55   $164.50  
  Purchase #2 $214.53   13.129%   $242.6956   $242.70   $242.70   $242.70  
  Purchase #3 $233.90   4.176%   $243.6677   $243.67   $243.65   $243.70  
  Purchase #4 $64.53   9.683%   $70.7784   $70.78   $70.80   $70.80  
  Purchase #5 $249.55   4.672%   $261.209   $261.21   $261.20   $261.20  
  Purchase #6 $21.29   13.735%   $24.2142   $24.21   $24.20   $24.20  
  Purchase #7 $9.67   8.145%   $10.4576   $10.46   $10.45   $10.50  
  7 purchase totals = $942.16       $1,017.5584   $1,017.57   $1,017.55   $1,017.60