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 $146.32   8.632%   $158.9503   $158.95   $158.95   $159.00  
  Purchase #2 $36.77   11.815%   $41.1144   $41.11   $41.10   $41.10  
  Purchase #3 $176.41   9.854%   $193.7934   $193.79   $193.80   $193.80  
  Purchase #4 $125.29   12.751%   $141.2657   $141.27   $141.25   $141.30  
  Purchase #5 $234.81   4.658%   $245.7474   $245.75   $245.75   $245.70  
  Purchase #6 $242.57   8.257%   $262.599   $262.60   $262.60   $262.60  
  Purchase #7 $142.69   11.128%   $158.5685   $158.57   $158.55   $158.60  
  7 purchase totals = $1,104.86       $1,202.0387   $1,202.04   $1,202.00   $1,202.10