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 $181.85   6.819%   $194.2504   $194.25   $194.25   $194.30  
  Purchase #2 $240.27   3.516%   $248.7179   $248.72   $248.70   $248.70  
  Purchase #3 $201.45   3.396%   $208.2912   $208.29   $208.30   $208.30  
  Purchase #4 $56.68   8.649%   $61.5823   $61.58   $61.60   $61.60  
  Purchase #5 $9.95   11.262%   $11.0706   $11.07   $11.05   $11.10  
  Purchase #6 $104.87   7.758%   $113.0058   $113.01   $113.00   $113.00  
  Purchase #7 $188.75   12.130%   $211.6454   $211.65   $211.65   $211.60  
  7 purchase totals = $983.82       $1,048.5636   $1,048.57   $1,048.55   $1,048.60