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 $181.96   5.654%   $192.248   $192.25   $192.25   $192.20  
  Purchase #2 $244.66   5.328%   $257.6955   $257.70   $257.70   $257.70  
  Purchase #3 $158.62   3.453%   $164.0971   $164.10   $164.10   $164.10  
  Purchase #4 $80.31   6.765%   $85.743   $85.74   $85.75   $85.70  
  Purchase #5 $94.80   4.806%   $99.3561   $99.36   $99.35   $99.40  
  Purchase #6 $214.64   8.110%   $232.0473   $232.05   $232.05   $232.00  
  Purchase #7 $240.95   5.591%   $254.4215   $254.42   $254.40   $254.40  
  7 purchase totals = $1,215.94       $1,285.6085   $1,285.62   $1,285.60   $1,285.50