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 $62.27   11.378%   $69.3551   $69.36   $69.35   $69.40  
  Purchase #2 $207.69   11.866%   $232.3345   $232.33   $232.35   $232.30  
  Purchase #3 $65.59   3.685%   $68.007   $68.01   $68.00   $68.00  
  Purchase #4 $232.66   8.415%   $252.2383   $252.24   $252.25   $252.20  
  Purchase #5 $204.86   10.686%   $226.7513   $226.75   $226.75   $226.80  
  Purchase #6 $230.99   9.196%   $252.2318   $252.23   $252.25   $252.20  
  Purchase #7 $127.77   8.548%   $138.6918   $138.69   $138.70   $138.70  
  7 purchase totals = $1,131.83       $1,239.6098   $1,239.61   $1,239.65   $1,239.60