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 $59.49   3.571%   $61.6144   $61.61   $61.60   $61.60  
  Purchase #2 $189.74   4.197%   $197.7034   $197.70   $197.70   $197.70  
  Purchase #3 $53.68   13.300%   $60.8194   $60.82   $60.80   $60.80  
  Purchase #4 $156.26   9.439%   $171.0094   $171.01   $171.00   $171.00  
  Purchase #5 $233.29   9.260%   $254.8927   $254.89   $254.90   $254.90  
  Purchase #6 $142.82   12.525%   $160.7082   $160.71   $160.70   $160.70  
  Purchase #7 $50.63   11.661%   $56.534   $56.53   $56.55   $56.50  
  7 purchase totals = $885.91       $963.2815   $963.27   $963.25   $963.20