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 $65.44   9.347%   $71.5567   $71.56   $71.55   $71.60  
  Purchase #2 $219.87   6.505%   $234.1725   $234.17   $234.15   $234.20  
  Purchase #3 $231.92   11.350%   $258.2429   $258.24   $258.25   $258.20  
  Purchase #4 $187.56   7.375%   $201.3926   $201.39   $201.40   $201.40  
  Purchase #5 $117.67   8.857%   $128.092   $128.09   $128.10   $128.10  
  Purchase #6 $227.53   6.493%   $242.3035   $242.30   $242.30   $242.30  
  Purchase #7 $243.92   6.501%   $259.7772   $259.78   $259.80   $259.80  
  7 purchase totals = $1,293.91       $1,395.5374   $1,395.53   $1,395.55   $1,395.60