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	$99.49	11.745%	$111.1751	$111.18	$111.20	$111.20
Purchase #2	$36.33	13.773%	$41.3337	$41.33	$41.35	$41.30
Purchase #3	$249.71	6.858%	$266.8351	$266.84	$266.85	$266.80
Purchase #4	$233.77	9.662%	$256.3569	$256.36	$256.35	$256.40
Purchase #5	$126.89	8.462%	$137.6274	$137.63	$137.65	$137.60
Purchase #6	$222.98	6.758%	$238.049	$238.05	$238.05	$238.00
Purchase #7	$86.72	6.792%	$92.61	$92.61	$92.60	$92.60
7 purchase totals =	$1,055.89		$1,143.9872	$1,144.00	$1,144.05	$1,143.90