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 $47.69   10.416%   $52.6574   $52.66   $52.65   $52.70  
  Purchase #2 $205.64   6.765%   $219.5515   $219.55   $219.55   $219.60  
  Purchase #3 $75.70   6.222%   $80.4101   $80.41   $80.40   $80.40  
  Purchase #4 $34.93   10.233%   $38.5044   $38.50   $38.50   $38.50  
  Purchase #5 $187.56   13.832%   $213.5033   $213.50   $213.50   $213.50  
  Purchase #6 $186.45   6.232%   $198.0696   $198.07   $198.05   $198.10  
  Purchase #7 $246.75   4.488%   $257.8241   $257.82   $257.80   $257.80  
  7 purchase totals = $984.72       $1,060.5204   $1,060.51   $1,060.45   $1,060.60