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 $126.45   5.733%   $133.6994   $133.70   $133.70   $133.70  
  Purchase #2 $31.91   13.118%   $36.096   $36.10   $36.10   $36.10  
  Purchase #3 $103.97   11.827%   $116.2665   $116.27   $116.25   $116.30  
  Purchase #4 $51.93   10.599%   $57.4341   $57.43   $57.45   $57.40  
  Purchase #5 $191.32   5.323%   $201.504   $201.50   $201.50   $201.50  
  Purchase #6 $166.56   4.351%   $173.807   $173.81   $173.80   $173.80  
  Purchase #7 $247.42   11.405%   $275.6383   $275.64   $275.65   $275.60  
  7 purchase totals = $919.56       $994.4453   $994.45   $994.45   $994.40