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	$42.70	6.388%	$45.4277	$45.43	$45.45	$45.40
Purchase #2	$100.72	11.128%	$111.9281	$111.93	$111.95	$111.90
Purchase #3	$81.44	4.326%	$84.9631	$84.96	$84.95	$85.00
Purchase #4	$214.77	7.730%	$231.3717	$231.37	$231.35	$231.40
Purchase #5	$238.39	4.228%	$248.4691	$248.47	$248.45	$248.50
Purchase #6	$127.33	11.716%	$142.248	$142.25	$142.25	$142.20
Purchase #7	$194.53	8.386%	$210.8433	$210.84	$210.85	$210.80
7 purchase totals =	$999.88		$1,075.2510	$1,075.25	$1,075.25	$1,075.20