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 $38.73   13.627%   $44.0077   $44.01   $44.00   $44.00  
  Purchase #2 $200.98   4.148%   $209.3167   $209.32   $209.30   $209.30  
  Purchase #3 $198.83   4.790%   $208.354   $208.35   $208.35   $208.40  
  Purchase #4 $198.37   10.751%   $219.6968   $219.70   $219.70   $219.70  
  Purchase #5 $174.76   12.569%   $196.7256   $196.73   $196.75   $196.70  
  Purchase #6 $184.88   3.865%   $192.0256   $192.03   $192.05   $192.00  
  Purchase #7 $169.69   4.556%   $177.4211   $177.42   $177.40   $177.40  
  7 purchase totals = $1,166.24       $1,247.5475   $1,247.56   $1,247.55   $1,247.50