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 $41.83   10.623%   $46.2736   $46.27   $46.25   $46.30  
  Purchase #2 $240.97   10.378%   $265.9779   $265.98   $266.00   $266.00  
  Purchase #3 $173.42   11.581%   $193.5038   $193.50   $193.50   $193.50  
  Purchase #4 $235.36   8.795%   $256.0599   $256.06   $256.05   $256.10  
  Purchase #5 $30.99   11.748%   $34.6307   $34.63   $34.65   $34.60  
  Purchase #6 $172.34   11.200%   $191.6421   $191.64   $191.65   $191.60  
  Purchase #7 $102.75   3.870%   $106.7264   $106.73   $106.75   $106.70  
  7 purchase totals = $997.66       $1,094.8144   $1,094.81   $1,094.85   $1,094.80