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 $208.25   4.303%   $217.211   $217.21   $217.20   $217.20  
  Purchase #2 $167.68   4.677%   $175.5224   $175.52   $175.50   $175.50  
  Purchase #3 $56.31   8.849%   $61.2929   $61.29   $61.30   $61.30  
  Purchase #4 $245.55   5.375%   $258.7483   $258.75   $258.75   $258.70  
  Purchase #5 $154.99   13.866%   $176.4809   $176.48   $176.50   $176.50  
  Purchase #6 $47.49   5.640%   $50.1684   $50.17   $50.15   $50.20  
  Purchase #7 $81.34   4.134%   $84.7026   $84.70   $84.70   $84.70  
  7 purchase totals = $961.61       $1,024.1265   $1,024.12   $1,024.10   $1,024.10