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 $59.28   5.297%   $62.4201   $62.42   $62.40   $62.40  
  Purchase #2 $176.67   10.693%   $195.5613   $195.56   $195.55   $195.60  
  Purchase #3 $81.38   6.479%   $86.6526   $86.65   $86.65   $86.70  
  Purchase #4 $96.40   12.408%   $108.3613   $108.36   $108.35   $108.40  
  Purchase #5 $211.82   12.335%   $237.948   $237.95   $237.95   $237.90  
  Purchase #6 $102.74   9.400%   $112.3976   $112.40   $112.40   $112.40  
  Purchase #7 $214.76   8.455%   $232.918   $232.92   $232.90   $232.90  
  7 purchase totals = $943.05       $1,036.2589   $1,036.26   $1,036.20   $1,036.30