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 $152.55   6.510%   $162.481   $162.48   $162.50   $162.50  
  Purchase #2 $247.70   8.868%   $269.666   $269.67   $269.65   $269.70  
  Purchase #3 $52.49   8.308%   $56.8509   $56.85   $56.85   $56.90  
  Purchase #4 $180.44   12.402%   $202.8182   $202.82   $202.80   $202.80  
  Purchase #5 $223.26   5.581%   $235.7201   $235.72   $235.70   $235.70  
  Purchase #6 $233.48   3.697%   $242.1118   $242.11   $242.10   $242.10  
  Purchase #7 $164.68   10.769%   $182.4144   $182.41   $182.40   $182.40  
  7 purchase totals = $1,254.60       $1,352.0624   $1,352.06   $1,352.00   $1,352.10