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 $210.78   8.486%   $228.6668   $228.67   $228.65   $228.70  
  Purchase #2 $205.76   4.751%   $215.5357   $215.54   $215.55   $215.50  
  Purchase #3 $65.94   5.247%   $69.3999   $69.40   $69.40   $69.40  
  Purchase #4 $198.92   8.109%   $215.0504   $215.05   $215.05   $215.10  
  Purchase #5 $129.78   3.548%   $134.3846   $134.38   $134.40   $134.40  
  Purchase #6 $39.58   5.389%   $41.713   $41.71   $41.70   $41.70  
  Purchase #7 $120.28   6.341%   $127.907   $127.91   $127.90   $127.90  
  7 purchase totals = $971.04       $1,032.6574   $1,032.66   $1,032.65   $1,032.70