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 $226.64   6.731%   $241.8951   $241.90   $241.90   $241.90  
  Purchase #2 $237.78   12.584%   $267.7022   $267.70   $267.70   $267.70  
  Purchase #3 $48.77   3.863%   $50.654   $50.65   $50.65   $50.70  
  Purchase #4 $230.72   9.167%   $251.8701   $251.87   $251.85   $251.90  
  Purchase #5 $209.93   12.363%   $235.8836   $235.88   $235.90   $235.90  
  Purchase #6 $37.32   11.275%   $41.5278   $41.53   $41.55   $41.50  
  Purchase #7 $57.62   11.756%   $64.3938   $64.39   $64.40   $64.40  
  7 purchase totals = $1,048.78       $1,153.9266   $1,153.92   $1,153.95   $1,154.00