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 $162.86   8.667%   $176.9751   $176.98   $177.00   $177.00  
  Purchase #2 $176.87   11.336%   $196.92   $196.92   $196.90   $196.90  
  Purchase #3 $161.77   8.483%   $175.4929   $175.49   $175.50   $175.50  
  Purchase #4 $151.85   6.675%   $161.986   $161.99   $162.00   $162.00  
  Purchase #5 $98.68   10.298%   $108.8421   $108.84   $108.85   $108.80  
  Purchase #6 $10.67   6.168%   $11.3281   $11.33   $11.35   $11.30  
  Purchase #7 $200.70   12.839%   $226.4679   $226.47   $226.45   $226.50  
  7 purchase totals = $963.40       $1,058.0121   $1,058.02   $1,058.05   $1,058.00