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 $202.91   4.298%   $211.6311   $211.63   $211.65   $211.60  
  Purchase #2 $22.40   13.385%   $25.3982   $25.40   $25.40   $25.40  
  Purchase #3 $10.99   7.195%   $11.7807   $11.78   $11.80   $11.80  
  Purchase #4 $52.91   3.553%   $54.7899   $54.79   $54.80   $54.80  
  Purchase #5 $248.62   9.728%   $272.8058   $272.81   $272.80   $272.80  
  Purchase #6 $161.85   4.737%   $169.5168   $169.52   $169.50   $169.50  
  Purchase #7 $167.73   8.564%   $182.0944   $182.09   $182.10   $182.10  
  7 purchase totals = $867.41       $928.0169   $928.02   $928.05   $928.00