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	$238.69	8.116%	$258.0621	$258.06	$258.05	$258.10
Purchase #2	$45.83	11.481%	$51.0917	$51.09	$51.10	$51.10
Purchase #3	$103.30	10.468%	$114.1134	$114.11	$114.10	$114.10
Purchase #4	$158.96	11.363%	$177.0226	$177.02	$177.00	$177.00
Purchase #5	$93.33	7.753%	$100.5659	$100.57	$100.55	$100.60
Purchase #6	$230.83	3.213%	$238.2466	$238.25	$238.25	$238.20
Purchase #7	$70.93	10.838%	$78.6174	$78.62	$78.60	$78.60
7 purchase totals =	$941.87		$1,017.7197	$1,017.72	$1,017.65	$1,017.70