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 $184.74   11.671%   $206.301   $206.30   $206.30   $206.30  
  Purchase #2 $127.52   3.795%   $132.3594   $132.36   $132.35   $132.40  
  Purchase #3 $80.70   8.704%   $87.7241   $87.72   $87.70   $87.70  
  Purchase #4 $113.74   5.158%   $119.6067   $119.61   $119.60   $119.60  
  Purchase #5 $185.60   6.839%   $198.2932   $198.29   $198.30   $198.30  
  Purchase #6 $216.73   12.367%   $243.533   $243.53   $243.55   $243.50  
  Purchase #7 $178.68   8.688%   $194.2037   $194.20   $194.20   $194.20  
  7 purchase totals = $1,087.71       $1,182.0211   $1,182.01   $1,182.00   $1,182.00