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 $89.41   7.289%   $95.9271   $95.93   $95.95   $95.90  
  Purchase #2 $180.43   5.608%   $190.5485   $190.55   $190.55   $190.50  
  Purchase #3 $243.55   13.332%   $276.0201   $276.02   $276.00   $276.00  
  Purchase #4 $202.80   7.524%   $218.0587   $218.06   $218.05   $218.10  
  Purchase #5 $144.59   9.161%   $157.8359   $157.84   $157.85   $157.80  
  Purchase #6 $181.86   5.789%   $192.3879   $192.39   $192.40   $192.40  
  Purchase #7 $51.99   8.467%   $56.392   $56.39   $56.40   $56.40  
  7 purchase totals = $1,094.63       $1,187.1702   $1,187.18   $1,187.20   $1,187.10