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 $215.32   9.260%   $235.2586   $235.26   $235.25   $235.30  
  Purchase #2 $235.42   13.370%   $266.8957   $266.90   $266.90   $266.90  
  Purchase #3 $73.72   10.663%   $81.5808   $81.58   $81.60   $81.60  
  Purchase #4 $66.99   8.695%   $72.8148   $72.81   $72.80   $72.80  
  Purchase #5 $17.38   10.297%   $19.1696   $19.17   $19.15   $19.20  
  Purchase #6 $169.35   8.671%   $184.0343   $184.03   $184.05   $184.00  
  Purchase #7 $164.65   7.739%   $177.3923   $177.39   $177.40   $177.40  
  7 purchase totals = $942.83       $1,037.1461   $1,037.14   $1,037.15   $1,037.20