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 $40.83   7.618%   $43.9404   $43.94   $43.95   $43.90  
  Purchase #2 $203.37   3.630%   $210.7523   $210.75   $210.75   $210.80  
  Purchase #3 $45.73   4.324%   $47.7074   $47.71   $47.70   $47.70  
  Purchase #4 $115.97   9.321%   $126.7796   $126.78   $126.80   $126.80  
  Purchase #5 $156.83   12.169%   $175.9146   $175.91   $175.90   $175.90  
  Purchase #6 $60.79   9.515%   $66.5742   $66.57   $66.55   $66.60  
  Purchase #7 $61.46   10.537%   $67.936   $67.94   $67.95   $67.90  
  7 purchase totals = $684.98       $739.6045   $739.60   $739.60   $739.60