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	$164.52	3.855%	$170.8622	$170.86	$170.85	$170.90
Purchase #2	$45.78	13.393%	$51.9113	$51.91	$51.90	$51.90
Purchase #3	$50.83	10.652%	$56.2444	$56.24	$56.25	$56.20
Purchase #4	$166.38	5.231%	$175.0833	$175.08	$175.10	$175.10
Purchase #5	$217.79	12.209%	$244.38	$244.38	$244.40	$244.40
Purchase #6	$104.32	12.274%	$117.1242	$117.12	$117.10	$117.10
Purchase #7	$194.51	4.836%	$203.9165	$203.92	$203.90	$203.90
7 purchase totals =	$944.13		$1,019.5219	$1,019.51	$1,019.50	$1,019.50