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 $214.41   6.357%   $228.04   $228.04   $228.05   $228.00  
  Purchase #2 $95.53   13.685%   $108.6033   $108.60   $108.60   $108.60  
  Purchase #3 $26.57   11.361%   $29.5886   $29.59   $29.60   $29.60  
  Purchase #4 $231.75   10.156%   $255.2865   $255.29   $255.30   $255.30  
  Purchase #5 $222.29   4.447%   $232.1752   $232.18   $232.20   $232.20  
  Purchase #6 $249.61   3.676%   $258.7857   $258.79   $258.80   $258.80  
  Purchase #7 $5.73   8.586%   $6.222   $6.22   $6.20   $6.20  
  7 purchase totals = $1,045.89       $1,118.7013   $1,118.71   $1,118.75   $1,118.70