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	$12.79	3.578%	$13.2476	$13.25	$13.25	$13.20
Purchase #2	$53.74	4.784%	$56.3109	$56.31	$56.30	$56.30
Purchase #3	$49.53	3.671%	$51.3482	$51.35	$51.35	$51.30
Purchase #4	$212.77	12.864%	$240.1407	$240.14	$240.15	$240.10
Purchase #5	$222.58	8.456%	$241.4014	$241.40	$241.40	$241.40
Purchase #6	$120.51	8.815%	$131.133	$131.13	$131.15	$131.10
Purchase #7	$241.72	12.154%	$271.0986	$271.10	$271.10	$271.10
7 purchase totals =	$913.64		$1,004.6804	$1,004.68	$1,004.70	$1,004.50