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 $143.92   7.491%   $154.701   $154.70   $154.70   $154.70  
  Purchase #2 $174.34   10.672%   $192.9456   $192.95   $192.95   $192.90  
  Purchase #3 $158.34   4.114%   $164.8541   $164.85   $164.85   $164.90  
  Purchase #4 $125.34   11.282%   $139.4809   $139.48   $139.50   $139.50  
  Purchase #5 $234.52   5.197%   $246.708   $246.71   $246.70   $246.70  
  Purchase #6 $46.91   7.399%   $50.3809   $50.38   $50.40   $50.40  
  Purchase #7 $140.77   4.308%   $146.8344   $146.83   $146.85   $146.80  
  7 purchase totals = $1,024.14       $1,095.9049   $1,095.90   $1,095.95   $1,095.90