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 $77.61   7.827%   $83.6845   $83.68   $83.70   $83.70  
  Purchase #2 $162.79   11.620%   $181.7062   $181.71   $181.70   $181.70  
  Purchase #3 $204.97   6.620%   $218.539   $218.54   $218.55   $218.50  
  Purchase #4 $230.99   13.244%   $261.5823   $261.58   $261.60   $261.60  
  Purchase #5 $139.26   3.352%   $143.928   $143.93   $143.95   $143.90  
  Purchase #6 $150.70   7.238%   $161.6077   $161.61   $161.60   $161.60  
  Purchase #7 $49.32   11.783%   $55.1314   $55.13   $55.15   $55.10  
  7 purchase totals = $1,015.64       $1,106.1791   $1,106.18   $1,106.25   $1,106.10