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 $180.76   7.296%   $193.9482   $193.95   $193.95   $193.90  
  Purchase #2 $210.43   10.228%   $231.9528   $231.95   $231.95   $232.00  
  Purchase #3 $225.72   3.729%   $234.1371   $234.14   $234.15   $234.10  
  Purchase #4 $197.91   10.458%   $218.6074   $218.61   $218.60   $218.60  
  Purchase #5 $11.60   9.372%   $12.6872   $12.69   $12.70   $12.70  
  Purchase #6 $230.71   4.820%   $241.8302   $241.83   $241.85   $241.80  
  Purchase #7 $248.37   13.338%   $281.4976   $281.50   $281.50   $281.50  
  7 purchase totals = $1,305.50       $1,414.6605   $1,414.67   $1,414.70   $1,414.60