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 $192.41   7.590%   $207.0139   $207.01   $207.00   $207.00  
  Purchase #2 $69.77   5.172%   $73.3785   $73.38   $73.40   $73.40  
  Purchase #3 $219.33   5.632%   $231.6827   $231.68   $231.70   $231.70  
  Purchase #4 $242.84   4.469%   $253.6925   $253.69   $253.70   $253.70  
  Purchase #5 $29.36   10.180%   $32.3488   $32.35   $32.35   $32.30  
  Purchase #6 $17.31   12.838%   $19.5323   $19.53   $19.55   $19.50  
  Purchase #7 $103.92   3.611%   $107.6726   $107.67   $107.65   $107.70  
  7 purchase totals = $874.94       $925.3213   $925.31   $925.35   $925.30