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 $63.90   9.159%   $69.7526   $69.75   $69.75   $69.80  
  Purchase #2 $171.54   4.495%   $179.2507   $179.25   $179.25   $179.30  
  Purchase #3 $200.27   9.120%   $218.5346   $218.53   $218.55   $218.50  
  Purchase #4 $227.67   11.114%   $252.9732   $252.97   $252.95   $253.00  
  Purchase #5 $180.81   13.387%   $205.015   $205.02   $205.00   $205.00  
  Purchase #6 $16.94   4.683%   $17.7333   $17.73   $17.75   $17.70  
  Purchase #7 $117.91   6.525%   $125.6036   $125.60   $125.60   $125.60  
  7 purchase totals = $979.04       $1,068.8630   $1,068.85   $1,068.85   $1,068.90