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 $106.46   3.535%   $110.2234   $110.22   $110.20   $110.20  
  Purchase #2 $98.85   3.706%   $102.5134   $102.51   $102.50   $102.50  
  Purchase #3 $232.92   12.813%   $262.764   $262.76   $262.75   $262.80  
  Purchase #4 $59.69   5.351%   $62.884   $62.88   $62.90   $62.90  
  Purchase #5 $214.58   3.398%   $221.8714   $221.87   $221.85   $221.90  
  Purchase #6 $66.74   9.546%   $73.111   $73.11   $73.10   $73.10  
  Purchase #7 $208.33   10.623%   $230.4609   $230.46   $230.45   $230.50  
  7 purchase totals = $987.57       $1,063.8281   $1,063.81   $1,063.75   $1,063.90