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 $71.28   6.770%   $76.1057   $76.11   $76.10   $76.10  
  Purchase #2 $173.59   9.569%   $190.2008   $190.20   $190.20   $190.20  
  Purchase #3 $67.77   10.172%   $74.6636   $74.66   $74.65   $74.70  
  Purchase #4 $176.41   11.291%   $196.3285   $196.33   $196.35   $196.30  
  Purchase #5 $171.53   13.404%   $194.5219   $194.52   $194.50   $194.50  
  Purchase #6 $189.96   12.201%   $213.137   $213.14   $213.15   $213.10  
  Purchase #7 $16.58   7.802%   $17.8736   $17.87   $17.85   $17.90  
  7 purchase totals = $867.12       $962.8311   $962.83   $962.80   $962.80