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 $212.46   9.366%   $232.359   $232.36   $232.35   $232.40  
  Purchase #2 $241.98   3.504%   $250.459   $250.46   $250.45   $250.50  
  Purchase #3 $91.61   6.579%   $97.637   $97.64   $97.65   $97.60  
  Purchase #4 $118.32   6.661%   $126.2013   $126.20   $126.20   $126.20  
  Purchase #5 $96.26   6.257%   $102.283   $102.28   $102.30   $102.30  
  Purchase #6 $23.47   10.235%   $25.8722   $25.87   $25.85   $25.90  
  Purchase #7 $214.37   10.539%   $236.9625   $236.96   $236.95   $237.00  
  7 purchase totals = $998.47       $1,071.7740   $1,071.77   $1,071.75   $1,071.90