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	$238.98	6.771%	$255.1613	$255.16	$255.15	$255.20
Purchase #2	$13.64	3.356%	$14.0978	$14.10	$14.10	$14.10
Purchase #3	$52.52	12.870%	$59.2793	$59.28	$59.30	$59.30
Purchase #4	$150.76	7.140%	$161.5243	$161.52	$161.50	$161.50
Purchase #5	$7.90	4.704%	$8.2716	$8.27	$8.25	$8.30
Purchase #6	$191.77	4.619%	$200.6279	$200.63	$200.65	$200.60
Purchase #7	$12.52	12.106%	$14.0357	$14.04	$14.05	$14.00
7 purchase totals =	$668.09		$712.9979	$713.00	$713.00	$713.00