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 $62.74   3.610%   $65.0049   $65.00   $65.00   $65.00  
  Purchase #2 $185.63   11.763%   $207.4657   $207.47   $207.45   $207.50  
  Purchase #3 $192.82   8.235%   $208.6987   $208.70   $208.70   $208.70  
  Purchase #4 $129.29   12.627%   $145.6154   $145.62   $145.60   $145.60  
  Purchase #5 $184.90   8.345%   $200.3299   $200.33   $200.35   $200.30  
  Purchase #6 $160.58   10.442%   $177.3478   $177.35   $177.35   $177.30  
  Purchase #7 $6.67   4.177%   $6.9486   $6.95   $6.95   $6.90  
  7 purchase totals = $922.63       $1,011.4110   $1,011.42   $1,011.40   $1,011.30