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 $191.54   7.386%   $205.6871   $205.69   $205.70   $205.70  
  Purchase #2 $184.38   12.592%   $207.5971   $207.60   $207.60   $207.60  
  Purchase #3 $116.27   7.493%   $124.9821   $124.98   $125.00   $125.00  
  Purchase #4 $8.60   12.293%   $9.6572   $9.66   $9.65   $9.70  
  Purchase #5 $238.81   12.629%   $268.9693   $268.97   $268.95   $269.00  
  Purchase #6 $223.80   5.166%   $235.3615   $235.36   $235.35   $235.40  
  Purchase #7 $184.37   11.862%   $206.24   $206.24   $206.25   $206.20  
  7 purchase totals = $1,147.77       $1,258.4943   $1,258.50   $1,258.50   $1,258.60