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	$62.69	7.334%	$67.2877	$67.29	$67.30	$67.30
Purchase #2	$94.41	5.754%	$99.8424	$99.84	$99.85	$99.80
Purchase #3	$109.36	6.109%	$116.0408	$116.04	$116.05	$116.00
Purchase #4	$144.63	4.783%	$151.5477	$151.55	$151.55	$151.50
Purchase #5	$142.37	5.233%	$149.8202	$149.82	$149.80	$149.80
Purchase #6	$9.44	12.757%	$10.6443	$10.64	$10.65	$10.60
Purchase #7	$237.37	8.793%	$258.2419	$258.24	$258.25	$258.20
7 purchase totals =	$800.27		$853.4250	$853.42	$853.45	$853.20