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	$118.80	10.384%	$131.1362	$131.14	$131.15	$131.10
Purchase #2	$178.37	6.634%	$190.2031	$190.20	$190.20	$190.20
Purchase #3	$220.57	9.341%	$241.1734	$241.17	$241.15	$241.20
Purchase #4	$42.38	3.346%	$43.798	$43.80	$43.80	$43.80
Purchase #5	$215.62	8.303%	$233.5229	$233.52	$233.50	$233.50
Purchase #6	$76.26	13.610%	$86.639	$86.64	$86.65	$86.60
Purchase #7	$61.86	8.671%	$67.2239	$67.22	$67.20	$67.20
7 purchase totals =	$913.86		$993.6965	$993.69	$993.65	$993.60