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 $222.48   4.294%   $232.0333   $232.03   $232.05   $232.00  
  Purchase #2 $231.99   3.313%   $239.6758   $239.68   $239.70   $239.70  
  Purchase #3 $66.40   4.547%   $69.4192   $69.42   $69.40   $69.40  
  Purchase #4 $209.72   3.519%   $217.1   $217.10   $217.10   $217.10  
  Purchase #5 $202.89   11.147%   $225.5061   $225.51   $225.50   $225.50  
  Purchase #6 $188.29   7.542%   $202.4908   $202.49   $202.50   $202.50  
  Purchase #7 $140.75   4.656%   $147.3033   $147.30   $147.30   $147.30  
  7 purchase totals = $1,262.52       $1,333.5285   $1,333.53   $1,333.55   $1,333.50