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	$108.67	7.319%	$116.6236	$116.62	$116.60	$116.60
Purchase #2	$165.40	5.680%	$174.7947	$174.79	$174.80	$174.80
Purchase #3	$228.58	6.470%	$243.3691	$243.37	$243.35	$243.40
Purchase #4	$230.94	4.607%	$241.5794	$241.58	$241.60	$241.60
Purchase #5	$88.93	12.732%	$100.2526	$100.25	$100.25	$100.30
Purchase #6	$48.90	11.686%	$54.6145	$54.61	$54.60	$54.60
Purchase #7	$112.52	8.869%	$122.4994	$122.50	$122.50	$122.50
7 purchase totals =	$983.94		$1,053.7333	$1,053.72	$1,053.70	$1,053.80