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 $50.99   13.864%   $58.0593   $58.06   $58.05   $58.10  
  Purchase #2 $226.26   5.387%   $238.4486   $238.45   $238.45   $238.40  
  Purchase #3 $87.91   11.366%   $97.9019   $97.90   $97.90   $97.90  
  Purchase #4 $166.71   9.123%   $181.919   $181.92   $181.90   $181.90  
  Purchase #5 $245.25   6.655%   $261.5714   $261.57   $261.55   $261.60  
  Purchase #6 $151.72   9.594%   $166.276   $166.28   $166.30   $166.30  
  Purchase #7 $213.82   3.562%   $221.4363   $221.44   $221.45   $221.40  
  7 purchase totals = $1,142.66       $1,225.6125   $1,225.62   $1,225.60   $1,225.60