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 $194.94   6.695%   $207.9912   $207.99   $208.00   $208.00  
  Purchase #2 $235.44   12.332%   $264.4745   $264.47   $264.45   $264.50  
  Purchase #3 $66.42   10.605%   $73.4638   $73.46   $73.45   $73.50  
  Purchase #4 $167.52   6.649%   $178.6584   $178.66   $178.65   $178.70  
  Purchase #5 $47.91   9.336%   $52.3829   $52.38   $52.40   $52.40  
  Purchase #6 $163.84   6.584%   $174.6272   $174.63   $174.65   $174.60  
  Purchase #7 $75.56   7.213%   $81.0101   $81.01   $81.00   $81.00  
  7 purchase totals = $951.63       $1,032.6081   $1,032.60   $1,032.60   $1,032.70