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 $118.55   6.328%   $126.0518   $126.05   $126.05   $126.10  
  Purchase #2 $38.54   6.649%   $41.1025   $41.10   $41.10   $41.10  
  Purchase #3 $7.35   8.478%   $7.9731   $7.97   $7.95   $8.00  
  Purchase #4 $207.55   8.182%   $224.5317   $224.53   $224.55   $224.50  
  Purchase #5 $241.59   5.244%   $254.259   $254.26   $254.25   $254.30  
  Purchase #6 $183.59   4.660%   $192.1453   $192.15   $192.15   $192.10  
  Purchase #7 $184.80   5.870%   $195.6478   $195.65   $195.65   $195.60  
  7 purchase totals = $981.97       $1,041.7112   $1,041.71   $1,041.70   $1,041.70