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 $218.26   9.551%   $239.106   $239.11   $239.10   $239.10  
  Purchase #2 $96.88   9.669%   $106.2473   $106.25   $106.25   $106.20  
  Purchase #3 $73.37   4.338%   $76.5528   $76.55   $76.55   $76.60  
  Purchase #4 $132.29   5.172%   $139.132   $139.13   $139.15   $139.10  
  Purchase #5 $216.39   9.168%   $236.2286   $236.23   $236.25   $236.20  
  Purchase #6 $118.50   11.226%   $131.8028   $131.80   $131.80   $131.80  
  Purchase #7 $246.35   6.477%   $262.3061   $262.31   $262.30   $262.30  
  7 purchase totals = $1,102.04       $1,191.3756   $1,191.38   $1,191.40   $1,191.30