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 $177.43   11.270%   $197.4264   $197.43   $197.45   $197.40  
  Purchase #2 $170.25   13.732%   $193.6287   $193.63   $193.65   $193.60  
  Purchase #3 $164.88   4.474%   $172.2567   $172.26   $172.25   $172.30  
  Purchase #4 $203.38   6.490%   $216.5794   $216.58   $216.60   $216.60  
  Purchase #5 $32.34   11.696%   $36.1225   $36.12   $36.10   $36.10  
  Purchase #6 $124.79   9.734%   $136.9371   $136.94   $136.95   $136.90  
  Purchase #7 $79.65   4.179%   $82.9786   $82.98   $83.00   $83.00  
  7 purchase totals = $952.72       $1,035.9294   $1,035.94   $1,036.00   $1,035.90