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	$165.96	9.249%	$181.3096	$181.31	$181.30	$181.30
Purchase #2	$49.37	10.402%	$54.5055	$54.51	$54.50	$54.50
Purchase #3	$195.80	10.756%	$216.8602	$216.86	$216.85	$216.90
Purchase #4	$237.31	9.451%	$259.7382	$259.74	$259.75	$259.70
Purchase #5	$55.76	6.718%	$59.506	$59.51	$59.50	$59.50
Purchase #6	$32.47	5.662%	$34.3085	$34.31	$34.30	$34.30
Purchase #7	$77.26	4.631%	$80.8379	$80.84	$80.85	$80.80
7 purchase totals =	$813.93		$887.0659	$887.08	$887.05	$887.00