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 $69.57   9.537%   $76.2049   $76.20   $76.20   $76.20  
  Purchase #2 $147.71   7.131%   $158.2432   $158.24   $158.25   $158.20  
  Purchase #3 $163.96   7.712%   $176.6046   $176.60   $176.60   $176.60  
  Purchase #4 $197.36   8.696%   $214.5224   $214.52   $214.50   $214.50  
  Purchase #5 $242.84   9.312%   $265.4533   $265.45   $265.45   $265.50  
  Purchase #6 $150.43   11.753%   $168.11   $168.11   $168.10   $168.10  
  Purchase #7 $21.44   6.533%   $22.8407   $22.84   $22.85   $22.80  
  7 purchase totals = $993.31       $1,081.9791   $1,081.96   $1,081.95   $1,081.90