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	$233.51	4.435%	$243.8662	$243.87	$243.85	$243.90
Purchase #2	$117.89	4.400%	$123.0772	$123.08	$123.10	$123.10
Purchase #3	$198.41	8.670%	$215.6121	$215.61	$215.60	$215.60
Purchase #4	$62.53	3.184%	$64.521	$64.52	$64.50	$64.50
Purchase #5	$50.84	6.494%	$54.1415	$54.14	$54.15	$54.10
Purchase #6	$145.52	12.358%	$163.5034	$163.50	$163.50	$163.50
Purchase #7	$238.89	10.630%	$264.284	$264.28	$264.30	$264.30
7 purchase totals =	$1,047.59		$1,129.0054	$1,129.00	$1,129.00	$1,129.00