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	$233.48	9.429%	$255.4948	$255.49	$255.50	$255.50
Purchase #2	$211.26	10.109%	$232.6163	$232.62	$232.60	$232.60
Purchase #3	$11.70	5.153%	$12.3029	$12.30	$12.30	$12.30
Purchase #4	$39.59	8.289%	$42.8716	$42.87	$42.85	$42.90
Purchase #5	$152.95	8.704%	$166.2628	$166.26	$166.25	$166.30
Purchase #6	$221.35	4.476%	$231.2576	$231.26	$231.25	$231.30
Purchase #7	$196.85	12.828%	$222.1019	$222.10	$222.10	$222.10
7 purchase totals =	$1,067.18		$1,162.9079	$1,162.90	$1,162.85	$1,163.00