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 $62.77   13.676%   $71.3544   $71.35   $71.35   $71.40  
  Purchase #2 $87.75   9.300%   $95.9108   $95.91   $95.90   $95.90  
  Purchase #3 $15.49   6.771%   $16.5388   $16.54   $16.55   $16.50  
  Purchase #4 $9.99   4.114%   $10.401   $10.40   $10.40   $10.40  
  Purchase #5 $141.83   3.335%   $146.56   $146.56   $146.55   $146.60  
  Purchase #6 $157.92   7.162%   $169.2302   $169.23   $169.25   $169.20  
  Purchase #7 $184.58   10.692%   $204.3153   $204.32   $204.30   $204.30  
  7 purchase totals = $660.33       $714.3105   $714.31   $714.30   $714.30