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 $73.87   5.867%   $78.204   $78.20   $78.20   $78.20  
  Purchase #2 $56.98   9.844%   $62.5891   $62.59   $62.60   $62.60  
  Purchase #3 $94.73   3.585%   $98.1261   $98.13   $98.15   $98.10  
  Purchase #4 $205.25   13.638%   $233.242   $233.24   $233.25   $233.20  
  Purchase #5 $246.81   3.173%   $254.6413   $254.64   $254.65   $254.60  
  Purchase #6 $44.88   5.562%   $47.3762   $47.38   $47.40   $47.40  
  Purchase #7 $246.62   5.179%   $259.3924   $259.39   $259.40   $259.40  
  7 purchase totals = $969.14       $1,033.5711   $1,033.57   $1,033.65   $1,033.50