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 $211.85   9.823%   $232.66   $232.66   $232.65   $232.70  
  Purchase #2 $77.68   11.734%   $86.795   $86.80   $86.80   $86.80  
  Purchase #3 $243.78   11.817%   $272.5875   $272.59   $272.60   $272.60  
  Purchase #4 $136.94   6.491%   $145.8288   $145.83   $145.85   $145.80  
  Purchase #5 $194.96   5.533%   $205.7471   $205.75   $205.75   $205.70  
  Purchase #6 $235.28   5.401%   $247.9875   $247.99   $248.00   $248.00  
  Purchase #7 $67.84   8.619%   $73.6871   $73.69   $73.70   $73.70  
  7 purchase totals = $1,168.33       $1,265.2930   $1,265.31   $1,265.35   $1,265.30