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	$236.33	3.274%	$244.0674	$244.07	$244.05	$244.10
Purchase #2	$159.49	3.847%	$165.6256	$165.63	$165.65	$165.60
Purchase #3	$237.52	12.155%	$266.3906	$266.39	$266.40	$266.40
Purchase #4	$40.91	4.569%	$42.7792	$42.78	$42.80	$42.80
Purchase #5	$87.31	4.798%	$91.4991	$91.50	$91.50	$91.50
Purchase #6	$190.43	12.685%	$214.586	$214.59	$214.60	$214.60
Purchase #7	$110.60	6.412%	$117.6917	$117.69	$117.70	$117.70
7 purchase totals =	$1,062.59		$1,142.6396	$1,142.65	$1,142.70	$1,142.70