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 $206.75   7.839%   $222.9571   $222.96   $222.95   $223.00  
  Purchase #2 $21.64   9.474%   $23.6902   $23.69   $23.70   $23.70  
  Purchase #3 $193.73   7.312%   $207.8955   $207.90   $207.90   $207.90  
  Purchase #4 $216.51   9.169%   $236.3618   $236.36   $236.35   $236.40  
  Purchase #5 $96.44   11.566%   $107.5943   $107.59   $107.60   $107.60  
  Purchase #6 $184.63   9.510%   $202.1883   $202.19   $202.20   $202.20  
  Purchase #7 $12.60   7.672%   $13.5667   $13.57   $13.55   $13.60  
  7 purchase totals = $932.30       $1,014.2539   $1,014.26   $1,014.25   $1,014.40