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 $104.64   4.772%   $109.6334   $109.63   $109.65   $109.60  
  Purchase #2 $172.96   13.319%   $195.9965   $196.00   $196.00   $196.00  
  Purchase #3 $237.51   10.565%   $262.6029   $262.60   $262.60   $262.60  
  Purchase #4 $213.54   13.493%   $242.353   $242.35   $242.35   $242.40  
  Purchase #5 $193.30   8.820%   $210.3491   $210.35   $210.35   $210.30  
  Purchase #6 $190.29   8.748%   $206.9366   $206.94   $206.95   $206.90  
  Purchase #7 $22.91   8.759%   $24.9167   $24.92   $24.90   $24.90  
  7 purchase totals = $1,135.15       $1,252.7882   $1,252.79   $1,252.80   $1,252.70