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 $224.37   10.555%   $248.0523   $248.05   $248.05   $248.10  
  Purchase #2 $212.99   4.352%   $222.2593   $222.26   $222.25   $222.30  
  Purchase #3 $232.78   5.820%   $246.3278   $246.33   $246.35   $246.30  
  Purchase #4 $144.27   8.518%   $156.5589   $156.56   $156.55   $156.60  
  Purchase #5 $68.48   11.166%   $76.1265   $76.13   $76.15   $76.10  
  Purchase #6 $241.75   11.416%   $269.3482   $269.35   $269.35   $269.30  
  Purchase #7 $16.52   13.747%   $18.791   $18.79   $18.80   $18.80  
  7 purchase totals = $1,141.16       $1,237.4640   $1,237.47   $1,237.50   $1,237.50