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 $62.96   4.186%   $65.5955   $65.60   $65.60   $65.60  
  Purchase #2 $194.70   5.548%   $205.502   $205.50   $205.50   $205.50  
  Purchase #3 $24.92   8.776%   $27.107   $27.11   $27.10   $27.10  
  Purchase #4 $62.54   11.165%   $69.5226   $69.52   $69.50   $69.50  
  Purchase #5 $227.54   8.797%   $247.5567   $247.56   $247.55   $247.60  
  Purchase #6 $26.59   13.302%   $30.127   $30.13   $30.15   $30.10  
  Purchase #7 $78.80   9.749%   $86.4822   $86.48   $86.50   $86.50  
  7 purchase totals = $678.05       $731.8930   $731.90   $731.90   $731.90