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 $68.85   3.119%   $70.9974   $71.00   $71.00   $71.00  
  Purchase #2 $76.44   11.841%   $85.4913   $85.49   $85.50   $85.50  
  Purchase #3 $203.27   4.105%   $211.6142   $211.61   $211.60   $211.60  
  Purchase #4 $36.77   12.800%   $41.4766   $41.48   $41.50   $41.50  
  Purchase #5 $199.84   9.838%   $219.5003   $219.50   $219.50   $219.50  
  Purchase #6 $24.84   7.121%   $26.6089   $26.61   $26.60   $26.60  
  Purchase #7 $212.44   8.385%   $230.2531   $230.25   $230.25   $230.30  
  7 purchase totals = $822.45       $885.9418   $885.94   $885.95   $886.00