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 $72.42   5.434%   $76.3553   $76.36   $76.35   $76.40  
  Purchase #2 $206.62   10.102%   $227.4928   $227.49   $227.50   $227.50  
  Purchase #3 $84.52   3.260%   $87.2754   $87.28   $87.30   $87.30  
  Purchase #4 $65.77   6.392%   $69.974   $69.97   $69.95   $70.00  
  Purchase #5 $121.62   3.538%   $125.9229   $125.92   $125.90   $125.90  
  Purchase #6 $210.45   11.773%   $235.2263   $235.23   $235.25   $235.20  
  Purchase #7 $212.68   11.533%   $237.2084   $237.21   $237.20   $237.20  
  7 purchase totals = $974.08       $1,059.4551   $1,059.46   $1,059.45   $1,059.50