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 $90.80   4.662%   $95.0331   $95.03   $95.05   $95.00  
  Purchase #2 $219.61   6.162%   $233.1424   $233.14   $233.15   $233.10  
  Purchase #3 $139.72   5.589%   $147.529   $147.53   $147.55   $147.50  
  Purchase #4 $205.94   3.860%   $213.8893   $213.89   $213.90   $213.90  
  Purchase #5 $97.97   11.278%   $109.0191   $109.02   $109.00   $109.00  
  Purchase #6 $166.42   4.730%   $174.2917   $174.29   $174.30   $174.30  
  Purchase #7 $9.74   13.610%   $11.0656   $11.07   $11.05   $11.10  
  7 purchase totals = $930.20       $983.9702   $983.97   $984.00   $983.90