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 $215.48   5.477%   $227.2818   $227.28   $227.30   $227.30  
  Purchase #2 $170.89   5.700%   $180.6307   $180.63   $180.65   $180.60  
  Purchase #3 $238.27   9.803%   $261.6276   $261.63   $261.65   $261.60  
  Purchase #4 $14.29   4.107%   $14.8769   $14.88   $14.90   $14.90  
  Purchase #5 $179.45   8.540%   $194.775   $194.78   $194.80   $194.80  
  Purchase #6 $202.50   9.667%   $222.0757   $222.08   $222.10   $222.10  
  Purchase #7 $127.81   5.305%   $134.5903   $134.59   $134.60   $134.60  
  7 purchase totals = $1,148.69       $1,235.8580   $1,235.87   $1,236.00   $1,235.90