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 $60.80   11.777%   $67.9604   $67.96   $67.95   $68.00  
  Purchase #2 $225.97   5.235%   $237.7995   $237.80   $237.80   $237.80  
  Purchase #3 $185.39   13.529%   $210.4714   $210.47   $210.45   $210.50  
  Purchase #4 $248.74   6.758%   $265.5498   $265.55   $265.55   $265.50  
  Purchase #5 $60.72   9.243%   $66.3323   $66.33   $66.35   $66.30  
  Purchase #6 $220.63   4.724%   $231.0526   $231.05   $231.05   $231.10  
  Purchase #7 $201.81   12.618%   $227.2744   $227.27   $227.25   $227.30  
  7 purchase totals = $1,204.06       $1,306.4404   $1,306.43   $1,306.40   $1,306.50