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 $232.37   7.645%   $250.1347   $250.13   $250.15   $250.10  
  Purchase #2 $174.95   5.289%   $184.2031   $184.20   $184.20   $184.20  
  Purchase #3 $215.37   12.282%   $241.8217   $241.82   $241.80   $241.80  
  Purchase #4 $106.36   3.491%   $110.073   $110.07   $110.05   $110.10  
  Purchase #5 $55.42   11.757%   $61.9357   $61.94   $61.95   $61.90  
  Purchase #6 $203.79   9.472%   $223.093   $223.09   $223.10   $223.10  
  Purchase #7 $23.81   4.184%   $24.8062   $24.81   $24.80   $24.80  
  7 purchase totals = $1,012.07       $1,096.0674   $1,096.06   $1,096.05   $1,096.00