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	$111.74	10.675%	$123.6682	$123.67	$123.65	$123.70
Purchase #2	$171.67	4.749%	$179.8226	$179.82	$179.80	$179.80
Purchase #3	$31.93	4.320%	$33.3094	$33.31	$33.30	$33.30
Purchase #4	$52.62	12.329%	$59.1075	$59.11	$59.10	$59.10
Purchase #5	$86.93	8.786%	$94.5677	$94.57	$94.55	$94.60
Purchase #6	$138.66	12.186%	$155.5571	$155.56	$155.55	$155.60
Purchase #7	$121.36	6.493%	$129.2399	$129.24	$129.25	$129.20
7 purchase totals =	$714.91		$775.2724	$775.28	$775.20	$775.30