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 $91.94   4.170%   $95.7739   $95.77   $95.75   $95.80  
  Purchase #2 $225.98   13.380%   $256.2161   $256.22   $256.20   $256.20  
  Purchase #3 $155.95   12.845%   $175.9818   $175.98   $176.00   $176.00  
  Purchase #4 $212.70   12.602%   $239.5045   $239.50   $239.50   $239.50  
  Purchase #5 $14.90   3.594%   $15.4355   $15.44   $15.45   $15.40  
  Purchase #6 $240.67   7.456%   $258.6144   $258.61   $258.60   $258.60  
  Purchase #7 $185.76   13.692%   $211.1943   $211.19   $211.20   $211.20  
  7 purchase totals = $1,127.90       $1,252.7205   $1,252.71   $1,252.70   $1,252.70