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 $201.66   6.692%   $215.1551   $215.16   $215.15   $215.20  
  Purchase #2 $73.96   3.635%   $76.6484   $76.65   $76.65   $76.60  
  Purchase #3 $147.25   11.172%   $163.7008   $163.70   $163.70   $163.70  
  Purchase #4 $144.64   5.151%   $152.0904   $152.09   $152.10   $152.10  
  Purchase #5 $31.60   9.133%   $34.486   $34.49   $34.50   $34.50  
  Purchase #6 $178.42   3.315%   $184.3346   $184.33   $184.35   $184.30  
  Purchase #7 $185.96   8.204%   $201.2162   $201.22   $201.20   $201.20  
  7 purchase totals = $963.49       $1,027.6315   $1,027.64   $1,027.65   $1,027.60