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 $196.66   10.715%   $217.7321   $217.73   $217.75   $217.70  
  Purchase #2 $160.51   9.371%   $175.5514   $175.55   $175.55   $175.60  
  Purchase #3 $27.44   8.315%   $29.7216   $29.72   $29.70   $29.70  
  Purchase #4 $190.38   6.631%   $203.0041   $203.00   $203.00   $203.00  
  Purchase #5 $72.74   4.726%   $76.1777   $76.18   $76.20   $76.20  
  Purchase #6 $219.76   12.196%   $246.5619   $246.56   $246.55   $246.60  
  Purchase #7 $191.91   8.674%   $208.5563   $208.56   $208.55   $208.60  
  7 purchase totals = $1,059.40       $1,157.3051   $1,157.30   $1,157.30   $1,157.40