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 $52.48   13.811%   $59.728   $59.73   $59.75   $59.70  
  Purchase #2 $127.75   4.613%   $133.6431   $133.64   $133.65   $133.60  
  Purchase #3 $241.75   8.665%   $262.6976   $262.70   $262.70   $262.70  
  Purchase #4 $212.77   8.593%   $231.0533   $231.05   $231.05   $231.10  
  Purchase #5 $69.75   6.453%   $74.251   $74.25   $74.25   $74.30  
  Purchase #6 $43.74   4.188%   $45.5718   $45.57   $45.55   $45.60  
  Purchase #7 $189.27   8.520%   $205.3958   $205.40   $205.40   $205.40  
  7 purchase totals = $937.51       $1,012.3406   $1,012.34   $1,012.35   $1,012.40