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 $176.68   5.841%   $186.9999   $187.00   $187.00   $187.00  
  Purchase #2 $196.29   5.466%   $207.0192   $207.02   $207.00   $207.00  
  Purchase #3 $5.67   11.705%   $6.3337   $6.33   $6.35   $6.30  
  Purchase #4 $185.87   5.325%   $195.7676   $195.77   $195.75   $195.80  
  Purchase #5 $118.44   13.108%   $133.9651   $133.97   $133.95   $134.00  
  Purchase #6 $241.78   13.827%   $275.2109   $275.21   $275.20   $275.20  
  Purchase #7 $195.99   9.177%   $213.976   $213.98   $214.00   $214.00  
  7 purchase totals = $1,120.72       $1,219.2724   $1,219.28   $1,219.25   $1,219.30