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	$154.51	7.605%	$166.2605	$166.26	$166.25	$166.30
Purchase #2	$62.77	13.277%	$71.104	$71.10	$71.10	$71.10
Purchase #3	$215.93	8.346%	$233.9515	$233.95	$233.95	$234.00
Purchase #4	$110.45	11.828%	$123.514	$123.51	$123.50	$123.50
Purchase #5	$167.51	9.516%	$183.4503	$183.45	$183.45	$183.50
Purchase #6	$152.37	6.504%	$162.2801	$162.28	$162.30	$162.30
Purchase #7	$225.75	5.486%	$238.1346	$238.13	$238.15	$238.10
7 purchase totals =	$1,089.29		$1,178.6950	$1,178.68	$1,178.70	$1,178.80