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 $195.60   6.265%   $207.8543   $207.85   $207.85   $207.90  
  Purchase #2 $9.69   3.296%   $10.0094   $10.01   $10.00   $10.00  
  Purchase #3 $150.33   6.239%   $159.7091   $159.71   $159.70   $159.70  
  Purchase #4 $240.92   10.461%   $266.1226   $266.12   $266.10   $266.10  
  Purchase #5 $193.78   5.678%   $204.7828   $204.78   $204.80   $204.80  
  Purchase #6 $139.39   11.688%   $155.6819   $155.68   $155.70   $155.70  
  Purchase #7 $61.42   3.256%   $63.4198   $63.42   $63.40   $63.40  
  7 purchase totals = $991.13       $1,067.5799   $1,067.57   $1,067.55   $1,067.60