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 $54.26   7.752%   $58.4662   $58.47   $58.45   $58.50  
  Purchase #2 $44.28   7.416%   $47.5638   $47.56   $47.55   $47.60  
  Purchase #3 $47.71   10.793%   $52.8593   $52.86   $52.85   $52.90  
  Purchase #4 $33.86   4.440%   $35.3634   $35.36   $35.35   $35.40  
  Purchase #5 $93.62   5.824%   $99.0724   $99.07   $99.05   $99.10  
  Purchase #6 $44.36   12.376%   $49.85   $49.85   $49.85   $49.90  
  Purchase #7 $19.59   13.119%   $22.16   $22.16   $22.15   $22.20  
  7 purchase totals = $337.68       $365.3351   $365.33   $365.25   $365.60