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 $186.67   5.621%   $197.1627   $197.16   $197.15   $197.20  
  Purchase #2 $61.45   6.353%   $65.3539   $65.35   $65.35   $65.40  
  Purchase #3 $132.45   11.259%   $147.3625   $147.36   $147.35   $147.40  
  Purchase #4 $25.37   5.697%   $26.8153   $26.82   $26.80   $26.80  
  Purchase #5 $237.63   12.630%   $267.6427   $267.64   $267.65   $267.60  
  Purchase #6 $246.99   8.865%   $268.8857   $268.89   $268.90   $268.90  
  Purchase #7 $70.52   7.859%   $76.0622   $76.06   $76.05   $76.10  
  7 purchase totals = $961.08       $1,049.2850   $1,049.28   $1,049.25   $1,049.40