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	$234.71	9.367%	$256.6953	$256.70	$256.70	$256.70
Purchase #2	$196.78	13.528%	$223.4004	$223.40	$223.40	$223.40
Purchase #3	$108.59	5.283%	$114.3268	$114.33	$114.35	$114.30
Purchase #4	$123.90	5.721%	$130.9883	$130.99	$131.00	$131.00
Purchase #5	$155.98	3.771%	$161.862	$161.86	$161.85	$161.90
Purchase #6	$180.79	10.779%	$200.2774	$200.28	$200.30	$200.30
Purchase #7	$53.47	11.429%	$59.5811	$59.58	$59.60	$59.60
7 purchase totals =	$1,054.22		$1,147.1313	$1,147.14	$1,147.20	$1,147.20