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 $44.49   9.183%   $48.5755   $48.58   $48.60   $48.60  
  Purchase #2 $190.90   10.713%   $211.3511   $211.35   $211.35   $211.40  
  Purchase #3 $205.94   10.794%   $228.1692   $228.17   $228.15   $228.20  
  Purchase #4 $160.62   9.253%   $175.4822   $175.48   $175.50   $175.50  
  Purchase #5 $47.80   13.120%   $54.0714   $54.07   $54.05   $54.10  
  Purchase #6 $192.57   5.740%   $203.6235   $203.62   $203.60   $203.60  
  Purchase #7 $244.99   6.565%   $261.0736   $261.07   $261.05   $261.10  
  7 purchase totals = $1,087.31       $1,182.3465   $1,182.34   $1,182.30   $1,182.50