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 $66.68   3.485%   $69.0038   $69.00   $69.00   $69.00  
  Purchase #2 $202.66   10.675%   $224.294   $224.29   $224.30   $224.30  
  Purchase #3 $104.93   13.686%   $119.2907   $119.29   $119.30   $119.30  
  Purchase #4 $147.77   9.643%   $162.0195   $162.02   $162.00   $162.00  
  Purchase #5 $222.87   11.558%   $248.6293   $248.63   $248.65   $248.60  
  Purchase #6 $141.25   10.385%   $155.9188   $155.92   $155.90   $155.90  
  Purchase #7 $47.61   13.801%   $54.1807   $54.18   $54.20   $54.20  
  7 purchase totals = $933.77       $1,033.3368   $1,033.33   $1,033.35   $1,033.30