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 $214.70   10.281%   $236.7733   $236.77   $236.75   $236.80  
  Purchase #2 $172.43   11.413%   $192.1094   $192.11   $192.10   $192.10  
  Purchase #3 $6.93   10.548%   $7.661   $7.66   $7.65   $7.70  
  Purchase #4 $113.69   9.508%   $124.4996   $124.50   $124.50   $124.50  
  Purchase #5 $95.68   12.576%   $107.7127   $107.71   $107.70   $107.70  
  Purchase #6 $240.38   12.138%   $269.5573   $269.56   $269.55   $269.60  
  Purchase #7 $178.78   5.476%   $188.57   $188.57   $188.55   $188.60  
  7 purchase totals = $1,022.59       $1,126.8833   $1,126.88   $1,126.80   $1,127.00