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 $201.82   8.834%   $219.6488   $219.65   $219.65   $219.60  
  Purchase #2 $153.37   7.759%   $165.27   $165.27   $165.25   $165.30  
  Purchase #3 $124.80   12.732%   $140.6895   $140.69   $140.70   $140.70  
  Purchase #4 $69.29   3.292%   $71.571   $71.57   $71.55   $71.60  
  Purchase #5 $106.38   9.249%   $116.2191   $116.22   $116.20   $116.20  
  Purchase #6 $245.91   6.537%   $261.9851   $261.99   $262.00   $262.00  
  Purchase #7 $164.67   8.591%   $178.8168   $178.82   $178.80   $178.80  
  7 purchase totals = $1,066.24       $1,154.2003   $1,154.21   $1,154.15   $1,154.20