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 $118.44   5.462%   $124.9092   $124.91   $124.90   $124.90  
  Purchase #2 $55.41   9.637%   $60.7499   $60.75   $60.75   $60.70  
  Purchase #3 $182.67   12.766%   $205.9897   $205.99   $206.00   $206.00  
  Purchase #4 $246.53   12.639%   $277.6889   $277.69   $277.70   $277.70  
  Purchase #5 $44.89   3.137%   $46.2982   $46.30   $46.30   $46.30  
  Purchase #6 $128.26   6.356%   $136.4122   $136.41   $136.40   $136.40  
  Purchase #7 $186.63   8.240%   $202.0083   $202.01   $202.00   $202.00  
  7 purchase totals = $962.83       $1,054.0564   $1,054.06   $1,054.05   $1,054.00