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 $228.50   10.581%   $252.6776   $252.68   $252.70   $252.70  
  Purchase #2 $185.73   13.605%   $210.9986   $211.00   $211.00   $211.00  
  Purchase #3 $47.73   12.707%   $53.7951   $53.80   $53.80   $53.80  
  Purchase #4 $43.89   6.258%   $46.6366   $46.64   $46.65   $46.60  
  Purchase #5 $184.78   4.203%   $192.5463   $192.55   $192.55   $192.50  
  Purchase #6 $204.74   10.211%   $225.646   $225.65   $225.65   $225.60  
  Purchase #7 $40.25   5.779%   $42.576   $42.58   $42.60   $42.60  
  7 purchase totals = $935.62       $1,024.8762   $1,024.90   $1,024.95   $1,024.80