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 $230.78   9.621%   $252.9833   $252.98   $253.00   $253.00  
  Purchase #2 $148.67   3.487%   $153.8541   $153.85   $153.85   $153.90  
  Purchase #3 $32.41   7.789%   $34.9344   $34.93   $34.95   $34.90  
  Purchase #4 $62.73   9.505%   $68.6925   $68.69   $68.70   $68.70  
  Purchase #5 $201.31   13.852%   $229.1955   $229.20   $229.20   $229.20  
  Purchase #6 $105.55   6.528%   $112.4403   $112.44   $112.45   $112.40  
  Purchase #7 $155.58   4.163%   $162.0568   $162.06   $162.05   $162.10  
  7 purchase totals = $937.03       $1,014.1569   $1,014.15   $1,014.20   $1,014.20