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 $42.25   10.691%   $46.7669   $46.77   $46.75   $46.80  
  Purchase #2 $144.60   4.570%   $151.2082   $151.21   $151.20   $151.20  
  Purchase #3 $242.37   6.274%   $257.5763   $257.58   $257.60   $257.60  
  Purchase #4 $219.57   7.777%   $236.646   $236.65   $236.65   $236.60  
  Purchase #5 $155.80   8.183%   $168.5491   $168.55   $168.55   $168.50  
  Purchase #6 $120.63   6.483%   $128.4504   $128.45   $128.45   $128.50  
  Purchase #7 $20.37   5.825%   $21.5566   $21.56   $21.55   $21.60  
  7 purchase totals = $945.59       $1,010.7535   $1,010.77   $1,010.75   $1,010.80