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 $180.29   13.161%   $204.018   $204.02   $204.00   $204.00  
  Purchase #2 $149.44   8.862%   $162.6834   $162.68   $162.70   $162.70  
  Purchase #3 $75.66   8.643%   $82.1993   $82.20   $82.20   $82.20  
  Purchase #4 $230.85   6.778%   $246.497   $246.50   $246.50   $246.50  
  Purchase #5 $187.45   9.169%   $204.6373   $204.64   $204.65   $204.60  
  Purchase #6 $200.95   11.396%   $223.8503   $223.85   $223.85   $223.90  
  Purchase #7 $73.59   10.568%   $81.367   $81.37   $81.35   $81.40  
  7 purchase totals = $1,098.23       $1,205.2523   $1,205.26   $1,205.25   $1,205.30