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 $121.84   3.662%   $126.3018   $126.30   $126.30   $126.30  
  Purchase #2 $87.71   10.577%   $96.9871   $96.99   $97.00   $97.00  
  Purchase #3 $73.91   11.471%   $82.3882   $82.39   $82.40   $82.40  
  Purchase #4 $187.25   8.806%   $203.7392   $203.74   $203.75   $203.70  
  Purchase #5 $250.79   5.834%   $265.4211   $265.42   $265.40   $265.40  
  Purchase #6 $162.46   6.811%   $173.5252   $173.53   $173.55   $173.50  
  Purchase #7 $192.65   11.523%   $214.8491   $214.85   $214.85   $214.80  
  7 purchase totals = $1,076.61       $1,163.2117   $1,163.22   $1,163.25   $1,163.10