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 $69.49   8.793%   $75.6003   $75.60   $75.60   $75.60  
  Purchase #2 $239.40   10.854%   $265.3845   $265.38   $265.40   $265.40  
  Purchase #3 $178.36   13.817%   $203.004   $203.00   $203.00   $203.00  
  Purchase #4 $10.62   6.428%   $11.3027   $11.30   $11.30   $11.30  
  Purchase #5 $109.33   4.783%   $114.5593   $114.56   $114.55   $114.60  
  Purchase #6 $211.87   12.531%   $238.4194   $238.42   $238.40   $238.40  
  Purchase #7 $146.50   12.797%   $165.2476   $165.25   $165.25   $165.20  
  7 purchase totals = $965.57       $1,073.5178   $1,073.51   $1,073.50   $1,073.50