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 $95.89   8.257%   $103.8076   $103.81   $103.80   $103.80  
  Purchase #2 $242.78   8.126%   $262.5083   $262.51   $262.50   $262.50  
  Purchase #3 $178.60   8.855%   $194.415   $194.42   $194.40   $194.40  
  Purchase #4 $142.41   6.859%   $152.1779   $152.18   $152.20   $152.20  
  Purchase #5 $121.98   8.699%   $132.591   $132.59   $132.60   $132.60  
  Purchase #6 $120.61   11.722%   $134.7479   $134.75   $134.75   $134.70  
  Purchase #7 $194.60   5.463%   $205.231   $205.23   $205.25   $205.20  
  7 purchase totals = $1,096.87       $1,185.4787   $1,185.49   $1,185.50   $1,185.40