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 $248.52   5.434%   $262.0246   $262.02   $262.00   $262.00  
  Purchase #2 $229.25   13.165%   $259.4308   $259.43   $259.45   $259.40  
  Purchase #3 $71.90   7.457%   $77.2616   $77.26   $77.25   $77.30  
  Purchase #4 $135.53   6.667%   $144.5658   $144.57   $144.55   $144.60  
  Purchase #5 $53.95   12.203%   $60.5335   $60.53   $60.55   $60.50  
  Purchase #6 $141.72   13.537%   $160.9046   $160.90   $160.90   $160.90  
  Purchase #7 $190.45   8.388%   $206.4249   $206.42   $206.40   $206.40  
  7 purchase totals = $1,071.32       $1,171.1458   $1,171.13   $1,171.10   $1,171.10