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 $193.86   4.198%   $201.9982   $202.00   $202.00   $202.00  
  Purchase #2 $34.76   13.204%   $39.3497   $39.35   $39.35   $39.30  
  Purchase #3 $178.74   5.509%   $188.5868   $188.59   $188.60   $188.60  
  Purchase #4 $204.39   4.801%   $214.2028   $214.20   $214.20   $214.20  
  Purchase #5 $135.74   8.607%   $147.4231   $147.42   $147.40   $147.40  
  Purchase #6 $174.83   12.464%   $196.6208   $196.62   $196.60   $196.60  
  Purchase #7 $34.90   4.598%   $36.5047   $36.50   $36.50   $36.50  
  7 purchase totals = $957.22       $1,024.6861   $1,024.68   $1,024.65   $1,024.60