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	$238.71	8.409%	$258.7831	$258.78	$258.80	$258.80
Purchase #2	$79.43	13.102%	$89.8369	$89.84	$89.85	$89.80
Purchase #3	$86.48	10.568%	$95.6192	$95.62	$95.60	$95.60
Purchase #4	$159.83	7.304%	$171.504	$171.50	$171.50	$171.50
Purchase #5	$88.65	8.571%	$96.2482	$96.25	$96.25	$96.20
Purchase #6	$196.55	10.848%	$217.8717	$217.87	$217.85	$217.90
Purchase #7	$231.52	4.744%	$242.5033	$242.50	$242.50	$242.50
7 purchase totals =	$1,081.17		$1,172.3664	$1,172.36	$1,172.35	$1,172.30