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 $206.48   9.300%   $225.6826   $225.68   $225.70   $225.70  
  Purchase #2 $134.30   4.376%   $140.177   $140.18   $140.20   $140.20  
  Purchase #3 $90.95   4.737%   $95.2583   $95.26   $95.25   $95.30  
  Purchase #4 $214.71   12.414%   $241.3641   $241.36   $241.35   $241.40  
  Purchase #5 $209.81   13.184%   $237.4714   $237.47   $237.45   $237.50  
  Purchase #6 $145.32   5.333%   $153.0699   $153.07   $153.05   $153.10  
  Purchase #7 $95.45   6.653%   $101.8003   $101.80   $101.80   $101.80  
  7 purchase totals = $1,097.02       $1,194.8236   $1,194.82   $1,194.80   $1,195.00