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 $93.47   10.735%   $103.504   $103.50   $103.50   $103.50  
  Purchase #2 $216.85   11.113%   $240.9485   $240.95   $240.95   $240.90  
  Purchase #3 $123.76   6.794%   $132.1683   $132.17   $132.15   $132.20  
  Purchase #4 $181.49   11.752%   $202.8187   $202.82   $202.80   $202.80  
  Purchase #5 $208.51   12.718%   $235.0283   $235.03   $235.05   $235.00  
  Purchase #6 $227.59   4.321%   $237.4242   $237.42   $237.40   $237.40  
  Purchase #7 $233.92   4.110%   $243.5341   $243.53   $243.55   $243.50  
  7 purchase totals = $1,285.59       $1,395.4261   $1,395.42   $1,395.40   $1,395.30