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 $250.79   4.618%   $262.3715   $262.37   $262.35   $262.40  
  Purchase #2 $226.99   11.575%   $253.2641   $253.26   $253.25   $253.30  
  Purchase #3 $144.46   9.736%   $158.5246   $158.52   $158.50   $158.50  
  Purchase #4 $240.82   7.258%   $258.2987   $258.30   $258.30   $258.30  
  Purchase #5 $68.89   6.292%   $73.2246   $73.22   $73.20   $73.20  
  Purchase #6 $59.99   6.109%   $63.6548   $63.65   $63.65   $63.70  
  Purchase #7 $32.55   6.275%   $34.5925   $34.59   $34.60   $34.60  
  7 purchase totals = $1,024.49       $1,103.9308   $1,103.91   $1,103.85   $1,104.00