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 $114.42   9.588%   $125.3906   $125.39   $125.40   $125.40  
  Purchase #2 $191.54   11.723%   $213.9942   $213.99   $214.00   $214.00  
  Purchase #3 $149.47   5.442%   $157.6042   $157.60   $157.60   $157.60  
  Purchase #4 $212.64   10.527%   $235.0246   $235.02   $235.00   $235.00  
  Purchase #5 $65.78   4.227%   $68.5605   $68.56   $68.55   $68.60  
  Purchase #6 $41.90   6.135%   $44.4706   $44.47   $44.45   $44.50  
  Purchase #7 $246.38   12.837%   $278.0078   $278.01   $278.00   $278.00  
  7 purchase totals = $1,022.13       $1,123.0525   $1,123.04   $1,123.00   $1,123.10