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	$146.85	8.147%	$158.8139	$158.81	$158.80	$158.80
Purchase #2	$16.77	8.528%	$18.2001	$18.20	$18.20	$18.20
Purchase #3	$38.29	12.751%	$43.1724	$43.17	$43.15	$43.20
Purchase #4	$118.84	7.856%	$128.1761	$128.18	$128.20	$128.20
Purchase #5	$230.69	4.427%	$240.9026	$240.90	$240.90	$240.90
Purchase #6	$42.78	9.299%	$46.7581	$46.76	$46.75	$46.80
Purchase #7	$86.37	3.427%	$89.3299	$89.33	$89.35	$89.30
7 purchase totals =	$680.59		$725.3531	$725.35	$725.35	$725.40