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 $114.59   10.235%   $126.3183   $126.32   $126.30   $126.30  
  Purchase #2 $169.72   8.622%   $184.3533   $184.35   $184.35   $184.40  
  Purchase #3 $165.81   10.344%   $182.9614   $182.96   $182.95   $183.00  
  Purchase #4 $175.71   3.176%   $181.2905   $181.29   $181.30   $181.30  
  Purchase #5 $87.48   13.729%   $99.4901   $99.49   $99.50   $99.50  
  Purchase #6 $117.89   3.693%   $122.2437   $122.24   $122.25   $122.20  
  Purchase #7 $163.94   9.433%   $179.4045   $179.40   $179.40   $179.40  
  7 purchase totals = $995.14       $1,076.0618   $1,076.05   $1,076.05   $1,076.10