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 $66.33   8.500%   $71.9681   $71.97   $71.95   $72.00  
  Purchase #2 $175.99   11.137%   $195.59   $195.59   $195.60   $195.60  
  Purchase #3 $70.97   11.321%   $79.0045   $79.00   $79.00   $79.00  
  Purchase #4 $71.34   8.598%   $77.4738   $77.47   $77.45   $77.50  
  Purchase #5 $126.26   9.292%   $137.9921   $137.99   $138.00   $138.00  
  Purchase #6 $114.61   10.393%   $126.5214   $126.52   $126.50   $126.50  
  Purchase #7 $83.51   4.289%   $87.0917   $87.09   $87.10   $87.10  
  7 purchase totals = $709.01       $775.6416   $775.63   $775.60   $775.70