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 $93.83   3.672%   $97.2754   $97.28   $97.30   $97.30  
  Purchase #2 $86.25   10.771%   $95.54   $95.54   $95.55   $95.50  
  Purchase #3 $76.98   6.282%   $81.8159   $81.82   $81.80   $81.80  
  Purchase #4 $214.29   10.285%   $236.3297   $236.33   $236.35   $236.30  
  Purchase #5 $208.59   10.526%   $230.5462   $230.55   $230.55   $230.50  
  Purchase #6 $242.66   10.697%   $268.6173   $268.62   $268.60   $268.60  
  Purchase #7 $206.55   4.593%   $216.0368   $216.04   $216.05   $216.00  
  7 purchase totals = $1,129.15       $1,226.1613   $1,226.18   $1,226.20   $1,226.00