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 $193.84   7.295%   $207.9806   $207.98   $208.00   $208.00  
  Purchase #2 $125.91   11.758%   $140.7145   $140.71   $140.70   $140.70  
  Purchase #3 $84.53   9.233%   $92.3347   $92.33   $92.35   $92.30  
  Purchase #4 $175.61   6.751%   $187.4654   $187.47   $187.45   $187.50  
  Purchase #5 $239.47   11.395%   $266.7576   $266.76   $266.75   $266.80  
  Purchase #6 $123.74   3.525%   $128.1018   $128.10   $128.10   $128.10  
  Purchase #7 $244.97   11.283%   $272.61   $272.61   $272.60   $272.60  
  7 purchase totals = $1,188.07       $1,295.9646   $1,295.96   $1,295.95   $1,296.00