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 $58.43   3.396%   $60.4143   $60.41   $60.40   $60.40  
  Purchase #2 $226.44   11.308%   $252.0458   $252.05   $252.05   $252.00  
  Purchase #3 $192.28   7.747%   $207.1759   $207.18   $207.20   $207.20  
  Purchase #4 $164.83   7.412%   $177.0472   $177.05   $177.05   $177.00  
  Purchase #5 $231.45   12.114%   $259.4879   $259.49   $259.50   $259.50  
  Purchase #6 $96.28   6.777%   $102.8049   $102.80   $102.80   $102.80  
  Purchase #7 $107.80   6.729%   $115.0539   $115.05   $115.05   $115.10  
  7 purchase totals = $1,077.51       $1,174.0299   $1,174.03   $1,174.05   $1,174.00