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 $59.69   8.453%   $64.7356   $64.74   $64.75   $64.70  
  Purchase #2 $168.64   9.522%   $184.6979   $184.70   $184.70   $184.70  
  Purchase #3 $101.61   8.669%   $110.4186   $110.42   $110.40   $110.40  
  Purchase #4 $213.58   12.143%   $239.515   $239.52   $239.50   $239.50  
  Purchase #5 $198.84   6.296%   $211.359   $211.36   $211.35   $211.40  
  Purchase #6 $32.49   11.387%   $36.1896   $36.19   $36.20   $36.20  
  Purchase #7 $8.57   9.123%   $9.3518   $9.35   $9.35   $9.40  
  7 purchase totals = $783.42       $856.2675   $856.28   $856.25   $856.30