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 $228.39   9.722%   $250.5941   $250.59   $250.60   $250.60  
  Purchase #2 $116.73   6.863%   $124.7412   $124.74   $124.75   $124.70  
  Purchase #3 $184.80   6.187%   $196.2336   $196.23   $196.25   $196.20  
  Purchase #4 $141.96   3.490%   $146.9144   $146.91   $146.90   $146.90  
  Purchase #5 $192.98   5.814%   $204.1999   $204.20   $204.20   $204.20  
  Purchase #6 $131.60   5.548%   $138.9012   $138.90   $138.90   $138.90  
  Purchase #7 $30.79   9.870%   $33.829   $33.83   $33.85   $33.80  
  7 purchase totals = $1,027.25       $1,095.4134   $1,095.40   $1,095.45   $1,095.30