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 $227.55   6.185%   $241.624   $241.62   $241.60   $241.60  
  Purchase #2 $213.30   5.487%   $225.0038   $225.00   $225.00   $225.00  
  Purchase #3 $27.83   8.109%   $30.0867   $30.09   $30.10   $30.10  
  Purchase #4 $220.75   6.791%   $235.7411   $235.74   $235.75   $235.70  
  Purchase #5 $56.33   3.705%   $58.417   $58.42   $58.40   $58.40  
  Purchase #6 $170.37   4.109%   $177.3705   $177.37   $177.35   $177.40  
  Purchase #7 $146.42   3.537%   $151.5989   $151.60   $151.60   $151.60  
  7 purchase totals = $1,062.55       $1,119.8420   $1,119.84   $1,119.80   $1,119.80