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 $61.34   3.403%   $63.4274   $63.43   $63.45   $63.40  
  Purchase #2 $201.64   10.561%   $222.9352   $222.94   $222.95   $222.90  
  Purchase #3 $53.42   13.662%   $60.7182   $60.72   $60.70   $60.70  
  Purchase #4 $213.55   13.471%   $242.3173   $242.32   $242.30   $242.30  
  Purchase #5 $237.81   5.477%   $250.8349   $250.83   $250.85   $250.80  
  Purchase #6 $180.35   4.534%   $188.5271   $188.53   $188.55   $188.50  
  Purchase #7 $243.94   4.202%   $254.1904   $254.19   $254.20   $254.20  
  7 purchase totals = $1,192.05       $1,282.9505   $1,282.96   $1,283.00   $1,282.80