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 $185.46   9.590%   $203.2456   $203.25   $203.25   $203.20  
  Purchase #2 $119.34   8.638%   $129.6486   $129.65   $129.65   $129.60  
  Purchase #3 $175.44   3.815%   $182.133   $182.13   $182.15   $182.10  
  Purchase #4 $69.51   3.451%   $71.9088   $71.91   $71.90   $71.90  
  Purchase #5 $136.42   6.545%   $145.3487   $145.35   $145.35   $145.30  
  Purchase #6 $177.69   8.676%   $193.1064   $193.11   $193.10   $193.10  
  Purchase #7 $165.33   8.195%   $178.8788   $178.88   $178.90   $178.90  
  7 purchase totals = $1,029.19       $1,104.2699   $1,104.28   $1,104.30   $1,104.10