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 $177.95   11.812%   $198.9695   $198.97   $198.95   $199.00  
  Purchase #2 $218.30   3.391%   $225.7026   $225.70   $225.70   $225.70  
  Purchase #3 $162.30   8.151%   $175.5291   $175.53   $175.55   $175.50  
  Purchase #4 $35.69   6.320%   $37.9456   $37.95   $37.95   $37.90  
  Purchase #5 $240.27   5.107%   $252.5406   $252.54   $252.55   $252.50  
  Purchase #6 $55.76   5.499%   $58.8262   $58.83   $58.85   $58.80  
  Purchase #7 $211.64   4.662%   $221.5067   $221.51   $221.50   $221.50  
  7 purchase totals = $1,101.91       $1,171.0203   $1,171.03   $1,171.05   $1,170.90