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 $174.74   13.187%   $197.783   $197.78   $197.80   $197.80  
  Purchase #2 $192.85   8.348%   $208.9491   $208.95   $208.95   $208.90  
  Purchase #3 $33.66   3.820%   $34.9458   $34.95   $34.95   $34.90  
  Purchase #4 $124.32   13.484%   $141.0833   $141.08   $141.10   $141.10  
  Purchase #5 $93.66   3.114%   $96.5766   $96.58   $96.60   $96.60  
  Purchase #6 $93.66   9.172%   $102.2505   $102.25   $102.25   $102.30  
  Purchase #7 $202.31   10.346%   $223.241   $223.24   $223.25   $223.20  
  7 purchase totals = $915.20       $1,004.8293   $1,004.83   $1,004.90   $1,004.80