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 $208.27   4.624%   $217.9004   $217.90   $217.90   $217.90  
  Purchase #2 $112.97   4.150%   $117.6583   $117.66   $117.65   $117.70  
  Purchase #3 $245.49   4.673%   $256.9617   $256.96   $256.95   $257.00  
  Purchase #4 $92.45   4.458%   $96.5714   $96.57   $96.55   $96.60  
  Purchase #5 $214.99   3.107%   $221.6697   $221.67   $221.65   $221.70  
  Purchase #6 $154.66   5.831%   $163.6782   $163.68   $163.70   $163.70  
  Purchase #7 $30.93   3.746%   $32.0886   $32.09   $32.10   $32.10  
  7 purchase totals = $1,059.76       $1,106.5283   $1,106.53   $1,106.50   $1,106.70