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 $58.50   5.463%   $61.6959   $61.70   $61.70   $61.70  
  Purchase #2 $108.76   13.454%   $123.3926   $123.39   $123.40   $123.40  
  Purchase #3 $112.42   12.196%   $126.1307   $126.13   $126.15   $126.10  
  Purchase #4 $144.70   13.277%   $163.9118   $163.91   $163.90   $163.90  
  Purchase #5 $139.46   13.127%   $157.7669   $157.77   $157.75   $157.80  
  Purchase #6 $212.56   8.616%   $230.8742   $230.87   $230.85   $230.90  
  Purchase #7 $194.53   3.767%   $201.8579   $201.86   $201.85   $201.90  
  7 purchase totals = $970.93       $1,065.6300   $1,065.63   $1,065.60   $1,065.70