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	$65.65	11.565%	$73.2424	$73.24	$73.25	$73.20
Purchase #2	$187.74	3.497%	$194.3053	$194.31	$194.30	$194.30
Purchase #3	$49.67	5.257%	$52.2812	$52.28	$52.30	$52.30
Purchase #4	$209.68	6.195%	$222.6697	$222.67	$222.65	$222.70
Purchase #5	$11.78	6.176%	$12.5075	$12.51	$12.50	$12.50
Purchase #6	$112.65	9.637%	$123.5061	$123.51	$123.50	$123.50
Purchase #7	$104.49	5.176%	$109.8984	$109.90	$109.90	$109.90
7 purchase totals =	$741.66		$788.4106	$788.42	$788.40	$788.40