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 $205.50   4.159%   $214.0467   $214.05   $214.05   $214.00  
  Purchase #2 $221.80   4.614%   $232.0339   $232.03   $232.05   $232.00  
  Purchase #3 $58.54   8.633%   $63.5938   $63.59   $63.60   $63.60  
  Purchase #4 $158.85   10.496%   $175.5229   $175.52   $175.50   $175.50  
  Purchase #5 $220.41   5.633%   $232.8257   $232.83   $232.85   $232.80  
  Purchase #6 $87.95   9.601%   $96.3941   $96.39   $96.40   $96.40  
  Purchase #7 $26.42   10.363%   $29.1579   $29.16   $29.15   $29.20  
  7 purchase totals = $979.47       $1,043.5750   $1,043.57   $1,043.60   $1,043.50