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 $66.93   13.517%   $75.9769   $75.98   $76.00   $76.00  
  Purchase #2 $16.77   5.427%   $17.6801   $17.68   $17.70   $17.70  
  Purchase #3 $228.61   10.640%   $252.9341   $252.93   $252.95   $252.90  
  Purchase #4 $166.30   6.796%   $177.6017   $177.60   $177.60   $177.60  
  Purchase #5 $210.59   10.833%   $233.4032   $233.40   $233.40   $233.40  
  Purchase #6 $243.84   9.632%   $267.3267   $267.33   $267.35   $267.30  
  Purchase #7 $130.76   10.190%   $144.0844   $144.08   $144.10   $144.10  
  7 purchase totals = $1,063.80       $1,169.0071   $1,169.00   $1,169.10   $1,169.00