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	$81.89	5.795%	$86.6355	$86.64	$86.65	$86.60
Purchase #2	$156.46	5.327%	$164.7946	$164.79	$164.80	$164.80
Purchase #3	$185.73	10.384%	$205.0162	$205.02	$205.00	$205.00
Purchase #4	$74.98	4.209%	$78.1359	$78.14	$78.15	$78.10
Purchase #5	$145.84	8.565%	$158.3312	$158.33	$158.35	$158.30
Purchase #6	$56.69	3.437%	$58.6384	$58.64	$58.65	$58.60
Purchase #7	$54.77	3.810%	$56.8567	$56.86	$56.85	$56.90
7 purchase totals =	$756.36		$808.4085	$808.42	$808.45	$808.30