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 $54.80   13.143%   $62.0024   $62.00   $62.00   $62.00  
  Purchase #2 $104.63   10.212%   $115.3148   $115.31   $115.30   $115.30  
  Purchase #3 $52.41   3.770%   $54.3859   $54.39   $54.40   $54.40  
  Purchase #4 $103.91   3.238%   $107.2746   $107.27   $107.25   $107.30  
  Purchase #5 $219.81   5.236%   $231.3193   $231.32   $231.30   $231.30  
  Purchase #6 $192.76   6.594%   $205.4706   $205.47   $205.45   $205.50  
  Purchase #7 $200.37   3.297%   $206.9762   $206.98   $207.00   $207.00  
  7 purchase totals = $928.69       $982.7438   $982.74   $982.70   $982.80