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 $152.64   8.757%   $166.0067   $166.01   $166.00   $166.00  
  Purchase #2 $73.68   6.263%   $78.2946   $78.29   $78.30   $78.30  
  Purchase #3 $176.63   12.697%   $199.0567   $199.06   $199.05   $199.10  
  Purchase #4 $248.32   11.432%   $276.7079   $276.71   $276.70   $276.70  
  Purchase #5 $113.67   4.252%   $118.5032   $118.50   $118.50   $118.50  
  Purchase #6 $212.46   5.360%   $223.8479   $223.85   $223.85   $223.80  
  Purchase #7 $177.32   3.112%   $182.8382   $182.84   $182.85   $182.80  
  7 purchase totals = $1,154.72       $1,245.2552   $1,245.26   $1,245.25   $1,245.20