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	$72.42	5.398%	$76.3292	$76.33	$76.35	$76.30
Purchase #2	$42.91	7.509%	$46.1321	$46.13	$46.15	$46.10
Purchase #3	$85.59	4.366%	$89.3269	$89.33	$89.35	$89.30
Purchase #4	$115.58	10.391%	$127.5899	$127.59	$127.60	$127.60
Purchase #5	$197.39	9.716%	$216.5684	$216.57	$216.55	$216.60
Purchase #6	$79.98	7.726%	$86.1593	$86.16	$86.15	$86.20
Purchase #7	$42.69	7.131%	$45.7342	$45.73	$45.75	$45.70
7 purchase totals =	$636.56		$687.8400	$687.84	$687.90	$687.80