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 $86.99   7.854%   $93.8222   $93.82   $93.80   $93.80  
  Purchase #2 $218.50   12.328%   $245.4367   $245.44   $245.45   $245.40  
  Purchase #3 $171.41   13.813%   $195.0869   $195.09   $195.10   $195.10  
  Purchase #4 $59.30   8.532%   $64.3595   $64.36   $64.35   $64.40  
  Purchase #5 $181.42   6.184%   $192.639   $192.64   $192.65   $192.60  
  Purchase #6 $214.53   8.630%   $233.0439   $233.04   $233.05   $233.00  
  Purchase #7 $48.97   5.383%   $51.6061   $51.61   $51.60   $51.60  
  7 purchase totals = $981.12       $1,075.9943   $1,076.00   $1,076.00   $1,075.90