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 $248.93   4.691%   $260.6073   $260.61   $260.60   $260.60  
  Purchase #2 $54.67   3.805%   $56.7502   $56.75   $56.75   $56.80  
  Purchase #3 $164.93   6.779%   $176.1106   $176.11   $176.10   $176.10  
  Purchase #4 $108.88   8.436%   $118.0651   $118.07   $118.05   $118.10  
  Purchase #5 $149.75   8.703%   $162.7827   $162.78   $162.80   $162.80  
  Purchase #6 $206.77   4.694%   $216.4758   $216.48   $216.50   $216.50  
  Purchase #7 $108.54   11.297%   $120.8018   $120.80   $120.80   $120.80  
  7 purchase totals = $1,042.47       $1,111.5935   $1,111.60   $1,111.60   $1,111.70