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 $61.29   13.578%   $69.612   $69.61   $69.60   $69.60  
  Purchase #2 $144.26   12.123%   $161.7486   $161.75   $161.75   $161.70  
  Purchase #3 $124.92   6.335%   $132.8337   $132.83   $132.85   $132.80  
  Purchase #4 $144.53   13.499%   $164.0401   $164.04   $164.05   $164.00  
  Purchase #5 $24.52   6.840%   $26.1972   $26.20   $26.20   $26.20  
  Purchase #6 $207.88   13.860%   $236.6922   $236.69   $236.70   $236.70  
  Purchase #7 $154.96   11.253%   $172.3976   $172.40   $172.40   $172.40  
  7 purchase totals = $862.36       $963.5214   $963.52   $963.55   $963.40