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 $91.91   4.686%   $96.2169   $96.22   $96.20   $96.20  
  Purchase #2 $231.82   13.197%   $262.4133   $262.41   $262.40   $262.40  
  Purchase #3 $172.86   13.804%   $196.7216   $196.72   $196.70   $196.70  
  Purchase #4 $193.84   4.409%   $202.3864   $202.39   $202.40   $202.40  
  Purchase #5 $218.50   3.532%   $226.2174   $226.22   $226.20   $226.20  
  Purchase #6 $201.73   11.367%   $224.6606   $224.66   $224.65   $224.70  
  Purchase #7 $214.95   4.685%   $225.0204   $225.02   $225.00   $225.00  
  7 purchase totals = $1,325.61       $1,433.6366   $1,433.64   $1,433.55   $1,433.60