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	$104.41	13.420%	$118.4218	$118.42	$118.40	$118.40
Purchase #2	$145.83	9.837%	$160.1753	$160.18	$160.20	$160.20
Purchase #3	$40.40	3.661%	$41.879	$41.88	$41.90	$41.90
Purchase #4	$28.61	3.591%	$29.6374	$29.64	$29.65	$29.60
Purchase #5	$40.69	13.673%	$46.2535	$46.25	$46.25	$46.30
Purchase #6	$85.69	10.656%	$94.8211	$94.82	$94.80	$94.80
Purchase #7	$228.58	4.359%	$238.5438	$238.54	$238.55	$238.50
7 purchase totals =	$674.21		$729.7319	$729.73	$729.75	$729.70