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 $219.36   3.415%   $226.8511   $226.85   $226.85   $226.90  
  Purchase #2 $250.77   4.456%   $261.9443   $261.94   $261.95   $261.90  
  Purchase #3 $95.62   4.186%   $99.6227   $99.62   $99.60   $99.60  
  Purchase #4 $25.85   3.123%   $26.6573   $26.66   $26.65   $26.70  
  Purchase #5 $163.72   5.726%   $173.0946   $173.09   $173.10   $173.10  
  Purchase #6 $232.51   7.176%   $249.1949   $249.19   $249.20   $249.20  
  Purchase #7 $62.56   11.530%   $69.7732   $69.77   $69.75   $69.80  
  7 purchase totals = $1,050.39       $1,107.1381   $1,107.12   $1,107.10   $1,107.20