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	$119.26	3.163%	$123.0322	$123.03	$123.05	$123.00
Purchase #2	$106.69	13.204%	$120.7773	$120.78	$120.80	$120.80
Purchase #3	$228.72	4.242%	$238.4223	$238.42	$238.40	$238.40
Purchase #4	$215.92	4.696%	$226.0596	$226.06	$226.05	$226.10
Purchase #5	$140.34	3.434%	$145.1593	$145.16	$145.15	$145.20
Purchase #6	$165.39	4.832%	$173.3816	$173.38	$173.40	$173.40
Purchase #7	$67.61	9.172%	$73.8112	$73.81	$73.80	$73.80
7 purchase totals =	$1,043.93		$1,100.6435	$1,100.64	$1,100.65	$1,100.70