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 $58.55   5.429%   $61.7287   $61.73   $61.75   $61.70  
  Purchase #2 $157.31   3.498%   $162.8127   $162.81   $162.80   $162.80  
  Purchase #3 $16.47   8.483%   $17.8672   $17.87   $17.85   $17.90  
  Purchase #4 $138.91   11.675%   $155.1277   $155.13   $155.15   $155.10  
  Purchase #5 $5.75   6.677%   $6.1339   $6.13   $6.15   $6.10  
  Purchase #6 $108.93   8.645%   $118.347   $118.35   $118.35   $118.30  
  Purchase #7 $227.73   5.574%   $240.4237   $240.42   $240.40   $240.40  
  7 purchase totals = $713.65       $762.4409   $762.44   $762.45   $762.30