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 $214.27   9.340%   $234.2828   $234.28   $234.30   $234.30  
  Purchase #2 $178.84   5.371%   $188.4455   $188.45   $188.45   $188.40  
  Purchase #3 $13.28   10.199%   $14.6344   $14.63   $14.65   $14.60  
  Purchase #4 $118.86   4.772%   $124.532   $124.53   $124.55   $124.50  
  Purchase #5 $232.77   7.590%   $250.4372   $250.44   $250.45   $250.40  
  Purchase #6 $193.88   5.235%   $204.0296   $204.03   $204.05   $204.00  
  Purchase #7 $118.39   7.859%   $127.6943   $127.69   $127.70   $127.70  
  7 purchase totals = $1,070.29       $1,144.0558   $1,144.05   $1,144.15   $1,143.90