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 $58.84   3.720%   $61.0288   $61.03   $61.05   $61.00  
  Purchase #2 $236.83   13.465%   $268.7192   $268.72   $268.70   $268.70  
  Purchase #3 $195.28   3.129%   $201.3903   $201.39   $201.40   $201.40  
  Purchase #4 $185.83   8.657%   $201.9173   $201.92   $201.90   $201.90  
  Purchase #5 $116.38   5.760%   $123.0835   $123.08   $123.10   $123.10  
  Purchase #6 $171.27   6.847%   $182.9969   $183.00   $183.00   $183.00  
  Purchase #7 $122.83   11.710%   $137.2134   $137.21   $137.20   $137.20  
  7 purchase totals = $1,087.26       $1,176.3494   $1,176.35   $1,176.35   $1,176.30