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 $41.54   6.400%   $44.1986   $44.20   $44.20   $44.20  
  Purchase #2 $171.49   7.584%   $184.4958   $184.50   $184.50   $184.50  
  Purchase #3 $163.46   7.489%   $175.7015   $175.70   $175.70   $175.70  
  Purchase #4 $103.31   7.282%   $110.833   $110.83   $110.85   $110.80  
  Purchase #5 $162.26   9.119%   $177.0565   $177.06   $177.05   $177.10  
  Purchase #6 $219.63   11.791%   $245.5266   $245.53   $245.55   $245.50  
  Purchase #7 $114.94   3.189%   $118.6054   $118.61   $118.60   $118.60  
  7 purchase totals = $976.63       $1,056.4174   $1,056.43   $1,056.45   $1,056.40