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 $71.95   6.524%   $76.644   $76.64   $76.65   $76.60  
  Purchase #2 $140.39   8.432%   $152.2277   $152.23   $152.25   $152.20  
  Purchase #3 $144.91   11.846%   $162.076   $162.08   $162.10   $162.10  
  Purchase #4 $236.25   12.229%   $265.141   $265.14   $265.15   $265.10  
  Purchase #5 $167.51   4.640%   $175.2825   $175.28   $175.30   $175.30  
  Purchase #6 $227.78   3.858%   $236.5678   $236.57   $236.55   $236.60  
  Purchase #7 $42.58   7.279%   $45.6794   $45.68   $45.70   $45.70  
  7 purchase totals = $1,031.37       $1,113.6184   $1,113.62   $1,113.70   $1,113.60