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 $63.25   13.777%   $71.964   $71.96   $71.95   $72.00  
  Purchase #2 $85.25   13.341%   $96.6232   $96.62   $96.60   $96.60  
  Purchase #3 $126.35   3.309%   $130.5309   $130.53   $130.55   $130.50  
  Purchase #4 $219.63   12.650%   $247.4132   $247.41   $247.40   $247.40  
  Purchase #5 $183.84   4.760%   $192.5908   $192.59   $192.60   $192.60  
  Purchase #6 $247.25   5.563%   $261.0045   $261.00   $261.00   $261.00  
  Purchase #7 $61.97   3.224%   $63.9679   $63.97   $63.95   $64.00  
  7 purchase totals = $987.54       $1,064.0945   $1,064.08   $1,064.05   $1,064.10