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	$57.96	6.141%	$61.5193	$61.52	$61.50	$61.50
Purchase #2	$102.78	10.566%	$113.6397	$113.64	$113.65	$113.60
Purchase #3	$92.40	13.704%	$105.0625	$105.06	$105.05	$105.10
Purchase #4	$229.62	5.284%	$241.7531	$241.75	$241.75	$241.80
Purchase #5	$109.86	4.626%	$114.9421	$114.94	$114.95	$114.90
Purchase #6	$205.93	7.479%	$221.3315	$221.33	$221.35	$221.30
Purchase #7	$139.77	6.841%	$149.3317	$149.33	$149.35	$149.30
7 purchase totals =	$938.32		$1,007.5799	$1,007.57	$1,007.60	$1,007.50