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 $152.99   9.563%   $167.6204   $167.62   $167.60   $167.60  
  Purchase #2 $211.55   11.305%   $235.4657   $235.47   $235.45   $235.50  
  Purchase #3 $20.36   3.464%   $21.0653   $21.07   $21.05   $21.10  
  Purchase #4 $64.79   5.798%   $68.5465   $68.55   $68.55   $68.50  
  Purchase #5 $125.71   11.310%   $139.9278   $139.93   $139.95   $139.90  
  Purchase #6 $235.58   7.126%   $252.3674   $252.37   $252.35   $252.40  
  Purchase #7 $232.43   6.589%   $247.7448   $247.74   $247.75   $247.70  
  7 purchase totals = $1,043.41       $1,132.7379   $1,132.75   $1,132.70   $1,132.70