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	$114.84	7.132%	$123.0304	$123.03	$123.05	$123.00
Purchase #2	$225.68	13.186%	$255.4382	$255.44	$255.45	$255.40
Purchase #3	$10.39	10.657%	$11.4973	$11.50	$11.50	$11.50
Purchase #4	$21.30	9.401%	$23.3024	$23.30	$23.30	$23.30
Purchase #5	$205.69	8.302%	$222.7664	$222.77	$222.75	$222.80
Purchase #6	$96.25	3.412%	$99.5341	$99.53	$99.55	$99.50
Purchase #7	$236.97	13.741%	$269.532	$269.53	$269.55	$269.50
7 purchase totals =	$911.12		$1,005.1008	$1,005.10	$1,005.15	$1,005.00