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 $84.90   13.118%   $96.0372   $96.04   $96.05   $96.00  
  Purchase #2 $146.45   8.371%   $158.7093   $158.71   $158.70   $158.70  
  Purchase #3 $213.84   9.628%   $234.4285   $234.43   $234.45   $234.40  
  Purchase #4 $158.52   10.102%   $174.5337   $174.53   $174.55   $174.50  
  Purchase #5 $177.49   13.284%   $201.0678   $201.07   $201.05   $201.10  
  Purchase #6 $154.49   12.501%   $173.8028   $173.80   $173.80   $173.80  
  Purchase #7 $114.92   12.148%   $128.8805   $128.88   $128.90   $128.90  
  7 purchase totals = $1,050.61       $1,167.4598   $1,167.46   $1,167.50   $1,167.40