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	$100.75	10.745%	$111.5756	$111.58	$111.60	$111.60
Purchase #2	$181.65	11.341%	$202.2509	$202.25	$202.25	$202.30
Purchase #3	$84.65	9.431%	$92.6333	$92.63	$92.65	$92.60
Purchase #4	$53.45	10.402%	$59.0099	$59.01	$59.00	$59.00
Purchase #5	$89.62	11.684%	$100.0912	$100.09	$100.10	$100.10
Purchase #6	$42.72	7.632%	$45.9804	$45.98	$46.00	$46.00
Purchase #7	$143.93	3.802%	$149.4022	$149.40	$149.40	$149.40
7 purchase totals =	$696.77		$760.9435	$760.94	$761.00	$761.00