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 $197.27   9.847%   $216.6952   $216.70   $216.70   $216.70  
  Purchase #2 $210.57   8.453%   $228.3695   $228.37   $228.35   $228.40  
  Purchase #3 $41.58   12.410%   $46.7401   $46.74   $46.75   $46.70  
  Purchase #4 $105.72   7.800%   $113.9662   $113.97   $113.95   $114.00  
  Purchase #5 $44.76   6.467%   $47.6546   $47.65   $47.65   $47.70  
  Purchase #6 $232.75   6.874%   $248.7492   $248.75   $248.75   $248.70  
  Purchase #7 $106.92   4.501%   $111.7325   $111.73   $111.75   $111.70  
  7 purchase totals = $939.57       $1,013.9073   $1,013.91   $1,013.90   $1,013.90