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	$164.56	13.773%	$187.2248	$187.22	$187.20	$187.20
Purchase #2	$96.71	13.137%	$109.4148	$109.41	$109.40	$109.40
Purchase #3	$60.49	4.566%	$63.252	$63.25	$63.25	$63.30
Purchase #4	$187.52	6.724%	$200.1288	$200.13	$200.15	$200.10
Purchase #5	$99.98	11.777%	$111.7546	$111.75	$111.75	$111.80
Purchase #6	$34.44	9.254%	$37.6271	$37.63	$37.65	$37.60
Purchase #7	$85.69	13.253%	$97.0465	$97.05	$97.05	$97.00
7 purchase totals =	$729.39		$806.4486	$806.44	$806.45	$806.40