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 $41.83   4.310%   $43.6329   $43.63   $43.65   $43.60  
  Purchase #2 $177.33   7.198%   $190.0942   $190.09   $190.10   $190.10  
  Purchase #3 $60.55   8.131%   $65.4733   $65.47   $65.45   $65.50  
  Purchase #4 $207.91   4.709%   $217.7005   $217.70   $217.70   $217.70  
  Purchase #5 $54.59   7.473%   $58.6695   $58.67   $58.65   $58.70  
  Purchase #6 $124.54   3.123%   $128.4294   $128.43   $128.45   $128.40  
  Purchase #7 $159.62   11.433%   $177.8694   $177.87   $177.85   $177.90  
  7 purchase totals = $826.37       $881.8692   $881.86   $881.85   $881.90