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 $214.35   10.238%   $236.2952   $236.30   $236.30   $236.30  
  Purchase #2 $238.59   3.323%   $246.5183   $246.52   $246.50   $246.50  
  Purchase #3 $248.35   13.819%   $282.6695   $282.67   $282.65   $282.70  
  Purchase #4 $23.65   12.866%   $26.6928   $26.69   $26.70   $26.70  
  Purchase #5 $57.91   13.405%   $65.6728   $65.67   $65.65   $65.70  
  Purchase #6 $142.63   3.280%   $147.3083   $147.31   $147.30   $147.30  
  Purchase #7 $234.71   11.666%   $262.0913   $262.09   $262.10   $262.10  
  7 purchase totals = $1,160.19       $1,267.2482   $1,267.25   $1,267.20   $1,267.30