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 $59.94   5.859%   $63.4519   $63.45   $63.45   $63.50  
  Purchase #2 $111.85   11.790%   $125.0371   $125.04   $125.05   $125.00  
  Purchase #3 $174.49   6.641%   $186.0779   $186.08   $186.10   $186.10  
  Purchase #4 $202.85   9.839%   $222.8084   $222.81   $222.80   $222.80  
  Purchase #5 $180.96   9.750%   $198.6036   $198.60   $198.60   $198.60  
  Purchase #6 $105.36   9.660%   $115.5378   $115.54   $115.55   $115.50  
  Purchase #7 $128.65   11.729%   $143.7394   $143.74   $143.75   $143.70  
  7 purchase totals = $964.10       $1,055.2561   $1,055.26   $1,055.30   $1,055.20