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 $52.53   13.432%   $59.5858   $59.59   $59.60   $59.60  
  Purchase #2 $215.66   4.853%   $226.126   $226.13   $226.15   $226.10  
  Purchase #3 $82.81   13.860%   $94.2875   $94.29   $94.30   $94.30  
  Purchase #4 $206.40   11.477%   $230.0885   $230.09   $230.10   $230.10  
  Purchase #5 $146.58   7.850%   $158.0865   $158.09   $158.10   $158.10  
  Purchase #6 $129.55   9.201%   $141.4699   $141.47   $141.45   $141.50  
  Purchase #7 $41.36   7.280%   $44.371   $44.37   $44.35   $44.40  
  7 purchase totals = $874.89       $954.0152   $954.03   $954.05   $954.10