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	$200.32	4.236%	$208.8056	$208.81	$208.80	$208.80
Purchase #2	$118.95	6.141%	$126.2547	$126.25	$126.25	$126.30
Purchase #3	$59.36	3.380%	$61.3664	$61.37	$61.35	$61.40
Purchase #4	$38.70	6.293%	$41.1354	$41.14	$41.15	$41.10
Purchase #5	$111.57	10.466%	$123.2469	$123.25	$123.25	$123.20
Purchase #6	$69.62	3.565%	$72.102	$72.10	$72.10	$72.10
Purchase #7	$250.68	8.104%	$270.9951	$271.00	$271.00	$271.00
7 purchase totals =	$849.20		$903.9061	$903.92	$903.90	$903.90