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 $169.83   7.432%   $182.4518   $182.45   $182.45   $182.50  
  Purchase #2 $165.97   11.231%   $184.6101   $184.61   $184.60   $184.60  
  Purchase #3 $67.44   8.716%   $73.3181   $73.32   $73.30   $73.30  
  Purchase #4 $222.34   6.274%   $236.2896   $236.29   $236.30   $236.30  
  Purchase #5 $168.97   11.432%   $188.2867   $188.29   $188.30   $188.30  
  Purchase #6 $241.45   7.292%   $259.0565   $259.06   $259.05   $259.10  
  Purchase #7 $36.94   6.173%   $39.2203   $39.22   $39.20   $39.20  
  7 purchase totals = $1,072.94       $1,163.2331   $1,163.24   $1,163.20   $1,163.30