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 $44.27   4.565%   $46.2909   $46.29   $46.30   $46.30  
  Purchase #2 $119.94   10.350%   $132.3538   $132.35   $132.35   $132.40  
  Purchase #3 $122.40   13.187%   $138.5409   $138.54   $138.55   $138.50  
  Purchase #4 $154.64   9.380%   $169.1452   $169.15   $169.15   $169.10  
  Purchase #5 $90.36   5.811%   $95.6108   $95.61   $95.60   $95.60  
  Purchase #6 $248.91   4.290%   $259.5882   $259.59   $259.60   $259.60  
  Purchase #7 $241.33   10.225%   $266.006   $266.01   $266.00   $266.00  
  7 purchase totals = $1,021.85       $1,107.5358   $1,107.54   $1,107.55   $1,107.50