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 $206.71   3.554%   $214.0565   $214.06   $214.05   $214.10  
  Purchase #2 $18.31   9.861%   $20.1155   $20.12   $20.10   $20.10  
  Purchase #3 $57.37   4.826%   $60.1387   $60.14   $60.15   $60.10  
  Purchase #4 $200.26   11.693%   $223.6764   $223.68   $223.70   $223.70  
  Purchase #5 $118.39   11.454%   $131.9504   $131.95   $131.95   $132.00  
  Purchase #6 $133.41   12.398%   $149.9502   $149.95   $149.95   $150.00  
  Purchase #7 $222.62   4.866%   $233.4527   $233.45   $233.45   $233.50  
  7 purchase totals = $957.07       $1,033.3404   $1,033.35   $1,033.35   $1,033.50