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 $32.48   4.701%   $34.0069   $34.01   $34.00   $34.00  
  Purchase #2 $176.47   13.849%   $200.9093   $200.91   $200.90   $200.90  
  Purchase #3 $65.85   3.763%   $68.3279   $68.33   $68.35   $68.30  
  Purchase #4 $44.36   4.618%   $46.4085   $46.41   $46.40   $46.40  
  Purchase #5 $205.60   8.575%   $223.2302   $223.23   $223.25   $223.20  
  Purchase #6 $163.86   11.110%   $182.0648   $182.06   $182.05   $182.10  
  Purchase #7 $237.55   10.615%   $262.7659   $262.77   $262.75   $262.80  
  7 purchase totals = $926.17       $1,017.7135   $1,017.72   $1,017.70   $1,017.70