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 $70.26   3.547%   $72.7521   $72.75   $72.75   $72.80  
  Purchase #2 $237.94   6.524%   $253.4632   $253.46   $253.45   $253.50  
  Purchase #3 $28.50   13.709%   $32.4071   $32.41   $32.40   $32.40  
  Purchase #4 $220.72   8.845%   $240.2427   $240.24   $240.25   $240.20  
  Purchase #5 $122.87   5.855%   $130.064   $130.06   $130.05   $130.10  
  Purchase #6 $93.43   3.556%   $96.7524   $96.75   $96.75   $96.80  
  Purchase #7 $214.97   6.668%   $229.3042   $229.30   $229.30   $229.30  
  7 purchase totals = $988.69       $1,054.9857   $1,054.97   $1,054.95   $1,055.10