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 $32.26   13.480%   $36.6086   $36.61   $36.60   $36.60  
  Purchase #2 $69.45   5.404%   $73.2031   $73.20   $73.20   $73.20  
  Purchase #3 $178.33   7.582%   $191.851   $191.85   $191.85   $191.90  
  Purchase #4 $158.54   9.451%   $173.5236   $173.52   $173.50   $173.50  
  Purchase #5 $57.94   10.775%   $64.183   $64.18   $64.20   $64.20  
  Purchase #6 $31.90   11.348%   $35.52   $35.52   $35.50   $35.50  
  Purchase #7 $171.99   8.589%   $186.7622   $186.76   $186.75   $186.80  
  7 purchase totals = $700.41       $761.6515   $761.64   $761.60   $761.70