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	$207.78	10.288%	$229.1564	$229.16	$229.15	$229.20
Purchase #2	$198.30	10.195%	$218.5167	$218.52	$218.50	$218.50
Purchase #3	$103.64	10.296%	$114.3108	$114.31	$114.30	$114.30
Purchase #4	$51.91	4.167%	$54.0731	$54.07	$54.05	$54.10
Purchase #5	$218.32	10.704%	$241.689	$241.69	$241.70	$241.70
Purchase #6	$42.35	10.492%	$46.7934	$46.79	$46.80	$46.80
Purchase #7	$175.65	3.354%	$181.5413	$181.54	$181.55	$181.50
7 purchase totals =	$997.95		$1,086.0807	$1,086.08	$1,086.05	$1,086.10