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 $182.64   10.692%   $202.1679   $202.17   $202.15   $202.20  
  Purchase #2 $88.28   8.297%   $95.6046   $95.60   $95.60   $95.60  
  Purchase #3 $182.71   10.504%   $201.9019   $201.90   $201.90   $201.90  
  Purchase #4 $112.38   13.478%   $127.5266   $127.53   $127.55   $127.50  
  Purchase #5 $248.81   7.154%   $266.6099   $266.61   $266.60   $266.60  
  Purchase #6 $50.39   11.370%   $56.1193   $56.12   $56.10   $56.10  
  Purchase #7 $60.58   7.773%   $65.2889   $65.29   $65.30   $65.30  
  7 purchase totals = $925.79       $1,015.2191   $1,015.22   $1,015.20   $1,015.20