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	$52.58	8.143%	$56.8616	$56.86	$56.85	$56.90
Purchase #2	$62.52	8.315%	$67.7185	$67.72	$67.70	$67.70
Purchase #3	$202.29	12.140%	$226.848	$226.85	$226.85	$226.80
Purchase #4	$89.64	7.834%	$96.6624	$96.66	$96.65	$96.70
Purchase #5	$233.77	4.445%	$244.1611	$244.16	$244.15	$244.20
Purchase #6	$45.77	5.168%	$48.1354	$48.14	$48.15	$48.10
Purchase #7	$33.93	10.435%	$37.4706	$37.47	$37.45	$37.50
7 purchase totals =	$720.50		$777.8576	$777.86	$777.80	$777.90