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 $95.86   5.813%   $101.4323   $101.43   $101.45   $101.40  
  Purchase #2 $185.69   10.596%   $205.3657   $205.37   $205.35   $205.40  
  Purchase #3 $77.92   10.431%   $86.0478   $86.05   $86.05   $86.00  
  Purchase #4 $182.52   12.172%   $204.7363   $204.74   $204.75   $204.70  
  Purchase #5 $16.99   7.338%   $18.2367   $18.24   $18.25   $18.20  
  Purchase #6 $214.27   5.389%   $225.817   $225.82   $225.80   $225.80  
  Purchase #7 $103.79   4.723%   $108.692   $108.69   $108.70   $108.70  
  7 purchase totals = $877.04       $950.3278   $950.34   $950.35   $950.20