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 $195.68   7.322%   $210.0077   $210.01   $210.00   $210.00  
  Purchase #2 $250.55   10.194%   $276.0911   $276.09   $276.10   $276.10  
  Purchase #3 $97.83   4.178%   $101.9173   $101.92   $101.90   $101.90  
  Purchase #4 $232.94   4.356%   $243.0869   $243.09   $243.10   $243.10  
  Purchase #5 $41.85   12.661%   $47.1486   $47.15   $47.15   $47.10  
  Purchase #6 $130.83   11.234%   $145.5274   $145.53   $145.55   $145.50  
  Purchase #7 $210.76   5.357%   $222.0504   $222.05   $222.05   $222.10  
  7 purchase totals = $1,160.44       $1,245.8294   $1,245.84   $1,245.85   $1,245.80