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 $232.78   12.830%   $262.6457   $262.65   $262.65   $262.60  
  Purchase #2 $192.85   8.224%   $208.71   $208.71   $208.70   $208.70  
  Purchase #3 $37.36   10.493%   $41.2802   $41.28   $41.30   $41.30  
  Purchase #4 $197.28   8.836%   $214.7117   $214.71   $214.70   $214.70  
  Purchase #5 $217.25   12.834%   $245.1319   $245.13   $245.15   $245.10  
  Purchase #6 $50.76   4.748%   $53.1701   $53.17   $53.15   $53.20  
  Purchase #7 $25.64   9.562%   $28.0917   $28.09   $28.10   $28.10  
  7 purchase totals = $953.92       $1,053.7413   $1,053.74   $1,053.75   $1,053.70