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 $231.68   5.430%   $244.2602   $244.26   $244.25   $244.30  
  Purchase #2 $56.68   4.113%   $59.0112   $59.01   $59.00   $59.00  
  Purchase #3 $188.50   7.484%   $202.6073   $202.61   $202.60   $202.60  
  Purchase #4 $126.42   13.295%   $143.2275   $143.23   $143.25   $143.20  
  Purchase #5 $127.73   11.785%   $142.783   $142.78   $142.80   $142.80  
  Purchase #6 $132.35   5.801%   $140.0276   $140.03   $140.05   $140.00  
  Purchase #7 $73.68   12.379%   $82.8008   $82.80   $82.80   $82.80  
  7 purchase totals = $937.04       $1,014.7176   $1,014.72   $1,014.75   $1,014.70