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 $167.26   5.566%   $176.5697   $176.57   $176.55   $176.60  
  Purchase #2 $171.94   7.154%   $184.2406   $184.24   $184.25   $184.20  
  Purchase #3 $62.37   12.583%   $70.218   $70.22   $70.20   $70.20  
  Purchase #4 $15.97   9.263%   $17.4493   $17.45   $17.45   $17.40  
  Purchase #5 $95.95   7.110%   $102.772   $102.77   $102.75   $102.80  
  Purchase #6 $154.91   12.863%   $174.8361   $174.84   $174.85   $174.80  
  Purchase #7 $26.44   12.766%   $29.8153   $29.82   $29.80   $29.80  
  7 purchase totals = $694.84       $755.9010   $755.91   $755.85   $755.80