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 $192.48   5.620%   $203.2974   $203.30   $203.30   $203.30  
  Purchase #2 $238.67   11.572%   $266.2889   $266.29   $266.30   $266.30  
  Purchase #3 $67.42   11.371%   $75.0863   $75.09   $75.10   $75.10  
  Purchase #4 $210.75   5.667%   $222.6932   $222.69   $222.70   $222.70  
  Purchase #5 $187.36   6.601%   $199.7276   $199.73   $199.75   $199.70  
  Purchase #6 $51.56   3.737%   $53.4868   $53.49   $53.50   $53.50  
  Purchase #7 $240.25   6.525%   $255.9263   $255.93   $255.95   $255.90  
  7 purchase totals = $1,188.49       $1,276.5065   $1,276.52   $1,276.60   $1,276.50