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 $34.51   5.372%   $36.3639   $36.36   $36.35   $36.40  
  Purchase #2 $193.46   4.765%   $202.6784   $202.68   $202.70   $202.70  
  Purchase #3 $109.37   12.115%   $122.6202   $122.62   $122.60   $122.60  
  Purchase #4 $166.59   9.470%   $182.3661   $182.37   $182.35   $182.40  
  Purchase #5 $230.88   8.774%   $251.1374   $251.14   $251.15   $251.10  
  Purchase #6 $234.82   4.382%   $245.1098   $245.11   $245.10   $245.10  
  Purchase #7 $109.69   11.671%   $122.4919   $122.49   $122.50   $122.50  
  7 purchase totals = $1,079.32       $1,162.7677   $1,162.77   $1,162.75   $1,162.80