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 $98.50   10.325%   $108.6701   $108.67   $108.65   $108.70  
  Purchase #2 $104.63   9.735%   $114.8157   $114.82   $114.80   $114.80  
  Purchase #3 $145.36   12.590%   $163.6608   $163.66   $163.65   $163.70  
  Purchase #4 $231.82   9.305%   $253.3909   $253.39   $253.40   $253.40  
  Purchase #5 $155.60   7.635%   $167.4801   $167.48   $167.50   $167.50  
  Purchase #6 $74.89   8.316%   $81.1179   $81.12   $81.10   $81.10  
  Purchase #7 $56.46   11.295%   $62.8372   $62.84   $62.85   $62.80  
  7 purchase totals = $867.26       $951.9727   $951.98   $951.95   $952.00