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 $191.81   7.625%   $206.4355   $206.44   $206.45   $206.40  
  Purchase #2 $175.94   7.282%   $188.752   $188.75   $188.75   $188.80  
  Purchase #3 $68.31   11.749%   $76.3357   $76.34   $76.35   $76.30  
  Purchase #4 $64.59   6.678%   $68.9033   $68.90   $68.90   $68.90  
  Purchase #5 $201.67   9.798%   $221.4296   $221.43   $221.45   $221.40  
  Purchase #6 $180.35   6.321%   $191.7499   $191.75   $191.75   $191.70  
  Purchase #7 $7.29   5.852%   $7.7166   $7.72   $7.70   $7.70  
  7 purchase totals = $889.96       $961.3226   $961.33   $961.35   $961.20