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 $239.55   11.726%   $267.6396   $267.64   $267.65   $267.60  
  Purchase #2 $99.59   9.760%   $109.31   $109.31   $109.30   $109.30  
  Purchase #3 $163.79   7.178%   $175.5468   $175.55   $175.55   $175.50  
  Purchase #4 $232.75   7.270%   $249.6709   $249.67   $249.65   $249.70  
  Purchase #5 $61.54   5.195%   $64.737   $64.74   $64.75   $64.70  
  Purchase #6 $85.32   10.811%   $94.5439   $94.54   $94.55   $94.50  
  Purchase #7 $51.50   3.811%   $53.4627   $53.46   $53.45   $53.50  
  7 purchase totals = $934.04       $1,014.9109   $1,014.91   $1,014.90   $1,014.80