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 $62.46   11.205%   $69.4586   $69.46   $69.45   $69.50  
  Purchase #2 $177.90   8.669%   $193.3222   $193.32   $193.30   $193.30  
  Purchase #3 $165.66   6.534%   $176.4842   $176.48   $176.50   $176.50  
  Purchase #4 $74.74   5.282%   $78.6878   $78.69   $78.70   $78.70  
  Purchase #5 $182.91   6.852%   $195.443   $195.44   $195.45   $195.40  
  Purchase #6 $130.57   10.220%   $143.9143   $143.91   $143.90   $143.90  
  Purchase #7 $135.51   13.285%   $153.5125   $153.51   $153.50   $153.50  
  7 purchase totals = $929.75       $1,010.8226   $1,010.81   $1,010.80   $1,010.80