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 $208.68   12.753%   $235.293   $235.29   $235.30   $235.30  
  Purchase #2 $14.74   5.375%   $15.5323   $15.53   $15.55   $15.50  
  Purchase #3 $8.64   6.257%   $9.1806   $9.18   $9.20   $9.20  
  Purchase #4 $207.57   6.134%   $220.3023   $220.30   $220.30   $220.30  
  Purchase #5 $22.40   4.119%   $23.3227   $23.32   $23.30   $23.30  
  Purchase #6 $242.97   4.260%   $253.3205   $253.32   $253.30   $253.30  
  Purchase #7 $8.54   5.870%   $9.0413   $9.04   $9.05   $9.00  
  7 purchase totals = $713.54       $765.9927   $765.98   $766.00   $765.90