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 $183.95   5.173%   $193.4657   $193.47   $193.45   $193.50  
  Purchase #2 $146.45   7.282%   $157.1145   $157.11   $157.10   $157.10  
  Purchase #3 $175.37   5.313%   $184.6874   $184.69   $184.70   $184.70  
  Purchase #4 $56.69   9.181%   $61.8947   $61.89   $61.90   $61.90  
  Purchase #5 $123.93   6.697%   $132.2296   $132.23   $132.25   $132.20  
  Purchase #6 $223.25   7.820%   $240.7082   $240.71   $240.70   $240.70  
  Purchase #7 $202.30   11.493%   $225.5503   $225.55   $225.55   $225.60  
  7 purchase totals = $1,111.94       $1,195.6504   $1,195.65   $1,195.65   $1,195.70