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 $129.33   13.412%   $146.6757   $146.68   $146.70   $146.70  
  Purchase #2 $164.28   10.761%   $181.9582   $181.96   $181.95   $182.00  
  Purchase #3 $248.43   3.573%   $257.3064   $257.31   $257.30   $257.30  
  Purchase #4 $97.93   7.477%   $105.2522   $105.25   $105.25   $105.30  
  Purchase #5 $118.55   4.774%   $124.2096   $124.21   $124.20   $124.20  
  Purchase #6 $197.86   8.483%   $214.6445   $214.64   $214.65   $214.60  
  Purchase #7 $92.31   4.209%   $96.1953   $96.20   $96.20   $96.20  
  7 purchase totals = $1,048.69       $1,126.2419   $1,126.25   $1,126.25   $1,126.30