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 $245.36   6.766%   $261.9611   $261.96   $261.95   $262.00  
  Purchase #2 $214.85   11.147%   $238.7993   $238.80   $238.80   $238.80  
  Purchase #3 $160.59   10.677%   $177.7362   $177.74   $177.75   $177.70  
  Purchase #4 $202.30   5.285%   $212.9916   $212.99   $213.00   $213.00  
  Purchase #5 $212.66   10.772%   $235.5677   $235.57   $235.55   $235.60  
  Purchase #6 $42.57   11.185%   $47.3315   $47.33   $47.35   $47.30  
  Purchase #7 $149.60   7.440%   $160.7302   $160.73   $160.75   $160.70  
  7 purchase totals = $1,227.93       $1,335.1176   $1,335.12   $1,335.15   $1,335.10