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	$238.43	5.328%	$251.1336	$251.13	$251.15	$251.10
Purchase #2	$61.74	6.232%	$65.5876	$65.59	$65.60	$65.60
Purchase #3	$118.78	7.433%	$127.6089	$127.61	$127.60	$127.60
Purchase #4	$97.34	6.445%	$103.6136	$103.61	$103.60	$103.60
Purchase #5	$183.66	8.200%	$198.7201	$198.72	$198.70	$198.70
Purchase #6	$187.49	11.408%	$208.8789	$208.88	$208.90	$208.90
Purchase #7	$59.92	7.446%	$64.3816	$64.38	$64.40	$64.40
7 purchase totals =	$947.36		$1,019.9243	$1,019.92	$1,019.95	$1,019.90