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	$83.80	12.341%	$94.1418	$94.14	$94.15	$94.10
Purchase #2	$138.87	4.771%	$145.4955	$145.50	$145.50	$145.50
Purchase #3	$145.28	8.154%	$157.1261	$157.13	$157.15	$157.10
Purchase #4	$42.70	8.478%	$46.3201	$46.32	$46.30	$46.30
Purchase #5	$83.69	3.343%	$86.4878	$86.49	$86.50	$86.50
Purchase #6	$81.57	9.410%	$89.2457	$89.25	$89.25	$89.20
Purchase #7	$113.97	4.258%	$118.8228	$118.82	$118.80	$118.80
7 purchase totals =	$689.88		$737.6398	$737.65	$737.65	$737.50