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 $161.49   8.533%   $175.2699   $175.27   $175.25   $175.30  
  Purchase #2 $98.66   5.758%   $104.3408   $104.34   $104.35   $104.30  
  Purchase #3 $181.92   5.289%   $191.5417   $191.54   $191.55   $191.50  
  Purchase #4 $35.49   9.218%   $38.7615   $38.76   $38.75   $38.80  
  Purchase #5 $37.27   6.696%   $39.7656   $39.77   $39.75   $39.80  
  Purchase #6 $151.55   8.590%   $164.5681   $164.57   $164.55   $164.60  
  Purchase #7 $145.35   8.716%   $158.0187   $158.02   $158.00   $158.00  
  7 purchase totals = $811.73       $872.2663   $872.27   $872.20   $872.30