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 $60.57   10.537%   $66.9523   $66.95   $66.95   $67.00  
  Purchase #2 $233.78   13.820%   $266.0884   $266.09   $266.10   $266.10  
  Purchase #3 $228.99   6.210%   $243.2103   $243.21   $243.20   $243.20  
  Purchase #4 $168.79   4.148%   $175.7914   $175.79   $175.80   $175.80  
  Purchase #5 $234.89   4.508%   $245.4788   $245.48   $245.50   $245.50  
  Purchase #6 $226.59   9.356%   $247.7898   $247.79   $247.80   $247.80  
  Purchase #7 $247.75   4.638%   $259.2406   $259.24   $259.25   $259.20  
  7 purchase totals = $1,401.36       $1,504.5516   $1,504.55   $1,504.60   $1,504.60