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 $190.49   4.748%   $199.5345   $199.53   $199.55   $199.50  
  Purchase #2 $214.71   9.426%   $234.9486   $234.95   $234.95   $234.90  
  Purchase #3 $212.84   7.248%   $228.2666   $228.27   $228.25   $228.30  
  Purchase #4 $200.84   5.235%   $211.354   $211.35   $211.35   $211.40  
  Purchase #5 $52.98   10.171%   $58.3686   $58.37   $58.35   $58.40  
  Purchase #6 $187.88   12.170%   $210.745   $210.75   $210.75   $210.70  
  Purchase #7 $189.35   6.381%   $201.4324   $201.43   $201.45   $201.40  
  7 purchase totals = $1,249.09       $1,344.6497   $1,344.65   $1,344.65   $1,344.60