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	$65.83	12.383%	$73.9817	$73.98	$74.00	$74.00
Purchase #2	$162.81	6.537%	$173.4529	$173.45	$173.45	$173.50
Purchase #3	$223.39	4.367%	$233.1454	$233.15	$233.15	$233.10
Purchase #4	$76.53	7.163%	$82.0118	$82.01	$82.00	$82.00
Purchase #5	$166.27	8.299%	$180.0687	$180.07	$180.05	$180.10
Purchase #6	$244.96	9.372%	$267.9177	$267.92	$267.90	$267.90
Purchase #7	$43.93	5.730%	$46.4472	$46.45	$46.45	$46.40
7 purchase totals =	$983.72		$1,057.0254	$1,057.03	$1,057.00	$1,057.00