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 $95.87   5.714%   $101.348   $101.35   $101.35   $101.30  
  Purchase #2 $232.59   6.298%   $247.2385   $247.24   $247.25   $247.20  
  Purchase #3 $164.89   11.299%   $183.5209   $183.52   $183.50   $183.50  
  Purchase #4 $227.79   13.219%   $257.9016   $257.90   $257.90   $257.90  
  Purchase #5 $91.64   3.747%   $95.0738   $95.07   $95.05   $95.10  
  Purchase #6 $237.58   12.529%   $267.3464   $267.35   $267.35   $267.30  
  Purchase #7 $247.98   13.870%   $282.3748   $282.37   $282.35   $282.40  
  7 purchase totals = $1,298.34       $1,434.8040   $1,434.80   $1,434.75   $1,434.70