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 $61.29   13.244%   $69.4072   $69.41   $69.40   $69.40  
  Purchase #2 $192.67   9.113%   $210.228   $210.23   $210.25   $210.20  
  Purchase #3 $197.84   9.671%   $216.9731   $216.97   $216.95   $217.00  
  Purchase #4 $245.88   12.252%   $276.0052   $276.01   $276.00   $276.00  
  Purchase #5 $163.35   9.788%   $179.3387   $179.34   $179.35   $179.30  
  Purchase #6 $171.63   12.772%   $193.5506   $193.55   $193.55   $193.60  
  Purchase #7 $153.81   4.615%   $160.9083   $160.91   $160.90   $160.90  
  7 purchase totals = $1,186.47       $1,306.4111   $1,306.42   $1,306.40   $1,306.40