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 $194.28   6.861%   $207.6096   $207.61   $207.60   $207.60  
  Purchase #2 $227.85   7.225%   $244.3122   $244.31   $244.30   $244.30  
  Purchase #3 $43.83   13.318%   $49.6673   $49.67   $49.65   $49.70  
  Purchase #4 $250.47   7.393%   $268.9872   $268.99   $269.00   $269.00  
  Purchase #5 $228.36   8.744%   $248.3278   $248.33   $248.35   $248.30  
  Purchase #6 $188.96   11.186%   $210.0971   $210.10   $210.10   $210.10  
  Purchase #7 $67.69   10.204%   $74.5971   $74.60   $74.60   $74.60  
  7 purchase totals = $1,201.44       $1,303.5983   $1,303.61   $1,303.60   $1,303.60