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 $108.29   6.701%   $115.5465   $115.55   $115.55   $115.50  
  Purchase #2 $11.25   5.159%   $11.8304   $11.83   $11.85   $11.80  
  Purchase #3 $92.39   4.269%   $96.3341   $96.33   $96.35   $96.30  
  Purchase #4 $54.41   3.829%   $56.4934   $56.49   $56.50   $56.50  
  Purchase #5 $160.32   11.255%   $178.364   $178.36   $178.35   $178.40  
  Purchase #6 $221.57   13.117%   $250.6333   $250.63   $250.65   $250.60  
  Purchase #7 $174.68   6.431%   $185.9137   $185.91   $185.90   $185.90  
  7 purchase totals = $822.91       $895.1154   $895.10   $895.15   $895.00