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 $63.91   8.350%   $69.2465   $69.25   $69.25   $69.20  
  Purchase #2 $192.83   11.167%   $214.3633   $214.36   $214.35   $214.40  
  Purchase #3 $141.69   4.132%   $147.5446   $147.54   $147.55   $147.50  
  Purchase #4 $55.71   11.384%   $62.052   $62.05   $62.05   $62.10  
  Purchase #5 $212.44   13.710%   $241.5655   $241.57   $241.55   $241.60  
  Purchase #6 $187.97   9.833%   $206.4531   $206.45   $206.45   $206.50  
  Purchase #7 $245.50   11.201%   $272.9985   $273.00   $273.00   $273.00  
  7 purchase totals = $1,100.05       $1,214.2235   $1,214.22   $1,214.20   $1,214.30