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 $44.89   8.134%   $48.5414   $48.54   $48.55   $48.50  
  Purchase #2 $244.36   8.182%   $264.3535   $264.35   $264.35   $264.40  
  Purchase #3 $174.88   13.195%   $197.9554   $197.96   $197.95   $198.00  
  Purchase #4 $243.37   6.500%   $259.1891   $259.19   $259.20   $259.20  
  Purchase #5 $31.36   5.855%   $33.1961   $33.20   $33.20   $33.20  
  Purchase #6 $8.28   3.561%   $8.5749   $8.57   $8.55   $8.60  
  Purchase #7 $247.54   7.157%   $265.2564   $265.26   $265.25   $265.30  
  7 purchase totals = $994.68       $1,077.0668   $1,077.07   $1,077.05   $1,077.20