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 $14.53   10.218%   $16.0147   $16.01   $16.00   $16.00  
  Purchase #2 $94.58   12.600%   $106.4971   $106.50   $106.50   $106.50  
  Purchase #3 $114.37   3.153%   $117.9761   $117.98   $118.00   $118.00  
  Purchase #4 $174.48   4.665%   $182.6195   $182.62   $182.60   $182.60  
  Purchase #5 $155.38   3.295%   $160.4998   $160.50   $160.50   $160.50  
  Purchase #6 $201.45   7.355%   $216.2666   $216.27   $216.25   $216.30  
  Purchase #7 $125.46   7.463%   $134.8231   $134.82   $134.80   $134.80  
  7 purchase totals = $880.25       $934.6969   $934.70   $934.65   $934.70