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 $168.25   4.433%   $175.7085   $175.71   $175.70   $175.70  
  Purchase #2 $104.49   13.227%   $118.3109   $118.31   $118.30   $118.30  
  Purchase #3 $158.38   11.559%   $176.6871   $176.69   $176.70   $176.70  
  Purchase #4 $121.74   13.823%   $138.5681   $138.57   $138.55   $138.60  
  Purchase #5 $179.62   9.799%   $197.221   $197.22   $197.20   $197.20  
  Purchase #6 $142.80   11.584%   $159.342   $159.34   $159.35   $159.30  
  Purchase #7 $247.75   4.336%   $258.4924   $258.49   $258.50   $258.50  
  7 purchase totals = $1,123.03       $1,224.3300   $1,224.33   $1,224.30   $1,224.30