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 $192.41   3.322%   $198.8019   $198.80   $198.80   $198.80  
  Purchase #2 $65.26   8.178%   $70.597   $70.60   $70.60   $70.60  
  Purchase #3 $68.75   11.740%   $76.8213   $76.82   $76.80   $76.80  
  Purchase #4 $151.62   7.142%   $162.4487   $162.45   $162.45   $162.40  
  Purchase #5 $112.93   12.436%   $126.974   $126.97   $126.95   $127.00  
  Purchase #6 $157.68   11.545%   $175.8842   $175.88   $175.90   $175.90  
  Purchase #7 $198.83   8.400%   $215.5317   $215.53   $215.55   $215.50  
  7 purchase totals = $947.48       $1,027.0588   $1,027.05   $1,027.05   $1,027.00