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 $84.59   8.792%   $92.0272   $92.03   $92.05   $92.00  
  Purchase #2 $246.38   8.489%   $267.2952   $267.30   $267.30   $267.30  
  Purchase #3 $116.96   5.551%   $123.4524   $123.45   $123.45   $123.50  
  Purchase #4 $73.86   11.163%   $82.105   $82.11   $82.10   $82.10  
  Purchase #5 $200.73   4.167%   $209.0944   $209.09   $209.10   $209.10  
  Purchase #6 $206.30   5.224%   $217.0771   $217.08   $217.10   $217.10  
  Purchase #7 $47.74   3.497%   $49.4095   $49.41   $49.40   $49.40  
  7 purchase totals = $976.56       $1,040.4608   $1,040.47   $1,040.50   $1,040.50