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 $94.96   13.320%   $107.6087   $107.61   $107.60   $107.60  
  Purchase #2 $75.44   4.264%   $78.6568   $78.66   $78.65   $78.70  
  Purchase #3 $230.97   6.514%   $246.0154   $246.02   $246.00   $246.00  
  Purchase #4 $240.78   11.763%   $269.103   $269.10   $269.10   $269.10  
  Purchase #5 $55.50   3.202%   $57.2771   $57.28   $57.30   $57.30  
  Purchase #6 $92.34   13.423%   $104.7348   $104.73   $104.75   $104.70  
  Purchase #7 $141.42   12.127%   $158.57   $158.57   $158.55   $158.60  
  7 purchase totals = $931.41       $1,021.9658   $1,021.97   $1,021.95   $1,022.00