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	$228.61	13.197%	$258.7797	$258.78	$258.80	$258.80
Purchase #2	$28.25	5.704%	$29.8614	$29.86	$29.85	$29.90
Purchase #3	$14.51	8.847%	$15.7937	$15.79	$15.80	$15.80
Purchase #4	$214.31	4.856%	$224.7169	$224.72	$224.70	$224.70
Purchase #5	$52.90	13.290%	$59.9304	$59.93	$59.95	$59.90
Purchase #6	$30.71	7.749%	$33.0897	$33.09	$33.10	$33.10
Purchase #7	$89.93	7.118%	$96.3312	$96.33	$96.35	$96.30
7 purchase totals =	$659.22		$718.5030	$718.50	$718.55	$718.50