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 $182.32   5.232%   $191.859   $191.86   $191.85   $191.90  
  Purchase #2 $6.41   5.480%   $6.7613   $6.76   $6.75   $6.80  
  Purchase #3 $73.57   12.606%   $82.8442   $82.84   $82.85   $82.80  
  Purchase #4 $107.99   7.305%   $115.8787   $115.88   $115.90   $115.90  
  Purchase #5 $152.52   4.582%   $159.5085   $159.51   $159.50   $159.50  
  Purchase #6 $234.64   12.705%   $264.451   $264.45   $264.45   $264.50  
  Purchase #7 $118.60   6.457%   $126.258   $126.26   $126.25   $126.30  
  7 purchase totals = $876.05       $947.5607   $947.56   $947.55   $947.70