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	$231.40	7.752%	$249.3381	$249.34	$249.35	$249.30
Purchase #2	$161.48	4.388%	$168.5657	$168.57	$168.55	$168.60
Purchase #3	$123.88	10.643%	$137.0645	$137.06	$137.05	$137.10
Purchase #4	$135.98	11.218%	$151.2342	$151.23	$151.25	$151.20
Purchase #5	$171.43	9.313%	$187.3953	$187.40	$187.40	$187.40
Purchase #6	$111.43	9.744%	$122.2877	$122.29	$122.30	$122.30
Purchase #7	$82.69	8.337%	$89.5839	$89.58	$89.60	$89.60
7 purchase totals =	$1,018.29		$1,105.4694	$1,105.47	$1,105.50	$1,105.50