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 $62.64   8.563%   $68.0039   $68.00   $68.00   $68.00  
  Purchase #2 $104.58   13.495%   $118.6931   $118.69   $118.70   $118.70  
  Purchase #3 $222.41   8.545%   $241.4149   $241.41   $241.40   $241.40  
  Purchase #4 $185.74   13.212%   $210.28   $210.28   $210.30   $210.30  
  Purchase #5 $147.35   11.618%   $164.4691   $164.47   $164.45   $164.50  
  Purchase #6 $191.71   8.785%   $208.5517   $208.55   $208.55   $208.60  
  Purchase #7 $94.98   11.253%   $105.6681   $105.67   $105.65   $105.70  
  7 purchase totals = $1,009.41       $1,117.0808   $1,117.07   $1,117.05   $1,117.20