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 $182.86   13.737%   $207.9795   $207.98   $208.00   $208.00  
  Purchase #2 $70.52   9.148%   $76.9712   $76.97   $76.95   $77.00  
  Purchase #3 $11.38   3.120%   $11.7351   $11.74   $11.75   $11.70  
  Purchase #4 $151.29   6.795%   $161.5702   $161.57   $161.55   $161.60  
  Purchase #5 $228.57   10.715%   $253.0613   $253.06   $253.05   $253.10  
  Purchase #6 $63.74   8.472%   $69.1401   $69.14   $69.15   $69.10  
  Purchase #7 $61.30   8.536%   $66.5326   $66.53   $66.55   $66.50  
  7 purchase totals = $769.66       $846.9900   $846.99   $847.00   $847.00