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 $182.96   10.592%   $202.3391   $202.34   $202.35   $202.30  
  Purchase #2 $180.60   8.611%   $196.1515   $196.15   $196.15   $196.20  
  Purchase #3 $186.36   11.727%   $208.2144   $208.21   $208.20   $208.20  
  Purchase #4 $189.55   12.313%   $212.8893   $212.89   $212.90   $212.90  
  Purchase #5 $21.67   12.627%   $24.4063   $24.41   $24.40   $24.40  
  Purchase #6 $158.46   3.485%   $163.9823   $163.98   $164.00   $164.00  
  Purchase #7 $31.66   12.197%   $35.5216   $35.52   $35.50   $35.50  
  7 purchase totals = $951.26       $1,043.5045   $1,043.50   $1,043.50   $1,043.50