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 $88.77   5.853%   $93.9657   $93.97   $93.95   $94.00  
  Purchase #2 $245.72   11.281%   $273.4397   $273.44   $273.45   $273.40  
  Purchase #3 $15.70   11.619%   $17.5242   $17.52   $17.50   $17.50  
  Purchase #4 $230.63   4.311%   $240.5725   $240.57   $240.55   $240.60  
  Purchase #5 $131.63   6.164%   $139.7437   $139.74   $139.75   $139.70  
  Purchase #6 $224.65   4.830%   $235.5006   $235.50   $235.50   $235.50  
  Purchase #7 $56.76   12.505%   $63.8578   $63.86   $63.85   $63.90  
  7 purchase totals = $993.86       $1,064.6042   $1,064.60   $1,064.55   $1,064.60