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 $86.36   11.595%   $96.3734   $96.37   $96.35   $96.40  
  Purchase #2 $68.69   7.861%   $74.0897   $74.09   $74.10   $74.10  
  Purchase #3 $199.44   6.636%   $212.6748   $212.67   $212.65   $212.70  
  Purchase #4 $111.97   6.635%   $119.3992   $119.40   $119.40   $119.40  
  Purchase #5 $152.84   6.457%   $162.7089   $162.71   $162.70   $162.70  
  Purchase #6 $198.30   5.259%   $208.7286   $208.73   $208.75   $208.70  
  Purchase #7 $186.52   12.712%   $210.2304   $210.23   $210.25   $210.20  
  7 purchase totals = $1,004.12       $1,084.2050   $1,084.20   $1,084.20   $1,084.20