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	$174.47	3.417%	$180.4316	$180.43	$180.45	$180.40
Purchase #2	$121.51	10.683%	$134.4909	$134.49	$134.50	$134.50
Purchase #3	$64.42	3.676%	$66.7881	$66.79	$66.80	$66.80
Purchase #4	$112.97	9.381%	$123.5677	$123.57	$123.55	$123.60
Purchase #5	$58.61	13.797%	$66.6964	$66.70	$66.70	$66.70
Purchase #6	$207.83	3.711%	$215.5426	$215.54	$215.55	$215.50
Purchase #7	$42.32	7.302%	$45.4102	$45.41	$45.40	$45.40
7 purchase totals =	$782.13		$832.9275	$832.93	$832.95	$832.90