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 $213.81   8.329%   $231.6182   $231.62   $231.60   $231.60  
  Purchase #2 $55.53   10.560%   $61.394   $61.39   $61.40   $61.40  
  Purchase #3 $17.30   4.648%   $18.1041   $18.10   $18.10   $18.10  
  Purchase #4 $157.65   5.331%   $166.0543   $166.05   $166.05   $166.10  
  Purchase #5 $152.34   9.145%   $166.2715   $166.27   $166.25   $166.30  
  Purchase #6 $187.81   5.133%   $197.4503   $197.45   $197.45   $197.50  
  Purchase #7 $220.26   6.533%   $234.6496   $234.65   $234.65   $234.60  
  7 purchase totals = $1,004.70       $1,075.5420   $1,075.53   $1,075.50   $1,075.60