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 $176.71   10.359%   $195.0154   $195.02   $195.00   $195.00  
  Purchase #2 $73.84   11.631%   $82.4283   $82.43   $82.45   $82.40  
  Purchase #3 $72.69   5.264%   $76.5164   $76.52   $76.50   $76.50  
  Purchase #4 $25.26   9.539%   $27.6696   $27.67   $27.65   $27.70  
  Purchase #5 $90.98   10.674%   $100.6912   $100.69   $100.70   $100.70  
  Purchase #6 $84.70   10.719%   $93.779   $93.78   $93.80   $93.80  
  Purchase #7 $176.88   13.439%   $200.6509   $200.65   $200.65   $200.70  
  7 purchase totals = $701.06       $776.7508   $776.76   $776.75   $776.80