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 $105.96   5.866%   $112.1756   $112.18   $112.20   $112.20  
  Purchase #2 $158.72   3.103%   $163.6451   $163.65   $163.65   $163.60  
  Purchase #3 $234.25   3.505%   $242.4605   $242.46   $242.45   $242.50  
  Purchase #4 $174.88   12.840%   $197.3346   $197.33   $197.35   $197.30  
  Purchase #5 $33.28   8.828%   $36.218   $36.22   $36.20   $36.20  
  Purchase #6 $193.44   5.324%   $203.7387   $203.74   $203.75   $203.70  
  Purchase #7 $71.76   8.535%   $77.8847   $77.88   $77.90   $77.90  
  7 purchase totals = $972.29       $1,033.4572   $1,033.46   $1,033.50   $1,033.40