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 $195.79   5.520%   $206.5976   $206.60   $206.60   $206.60  
  Purchase #2 $67.41   13.466%   $76.4874   $76.49   $76.50   $76.50  
  Purchase #3 $53.74   4.194%   $55.9939   $55.99   $56.00   $56.00  
  Purchase #4 $209.39   4.196%   $218.176   $218.18   $218.20   $218.20  
  Purchase #5 $238.89   6.186%   $253.6677   $253.67   $253.65   $253.70  
  Purchase #6 $42.95   6.874%   $45.9024   $45.90   $45.90   $45.90  
  Purchase #7 $54.52   10.324%   $60.1486   $60.15   $60.15   $60.10  
  7 purchase totals = $862.69       $916.9736   $916.98   $917.00   $917.00