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 $195.46   5.258%   $205.7373   $205.74   $205.75   $205.70  
  Purchase #2 $247.25   7.559%   $265.9396   $265.94   $265.95   $265.90  
  Purchase #3 $230.29   12.719%   $259.5806   $259.58   $259.60   $259.60  
  Purchase #4 $208.51   11.523%   $232.5366   $232.54   $232.55   $232.50  
  Purchase #5 $195.46   13.203%   $221.2666   $221.27   $221.25   $221.30  
  Purchase #6 $193.84   3.827%   $201.2583   $201.26   $201.25   $201.30  
  Purchase #7 $64.66   7.317%   $69.3912   $69.39   $69.40   $69.40  
  7 purchase totals = $1,335.47       $1,455.7102   $1,455.72   $1,455.75   $1,455.70