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 $144.33   5.447%   $152.1917   $152.19   $152.20   $152.20  
  Purchase #2 $177.89   8.555%   $193.1085   $193.11   $193.10   $193.10  
  Purchase #3 $33.88   7.779%   $36.5155   $36.52   $36.50   $36.50  
  Purchase #4 $219.74   9.745%   $241.1537   $241.15   $241.15   $241.20  
  Purchase #5 $99.37   9.311%   $108.6223   $108.62   $108.60   $108.60  
  Purchase #6 $40.89   6.459%   $43.5311   $43.53   $43.55   $43.50  
  Purchase #7 $171.33   9.115%   $186.9467   $186.95   $186.95   $186.90  
  7 purchase totals = $887.43       $962.0695   $962.07   $962.05   $962.00