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	$90.65	12.257%	$101.761	$101.76	$101.75	$101.80
Purchase #2	$196.76	6.429%	$209.4097	$209.41	$209.40	$209.40
Purchase #3	$225.75	3.557%	$233.7799	$233.78	$233.80	$233.80
Purchase #4	$187.51	4.596%	$196.128	$196.13	$196.15	$196.10
Purchase #5	$49.83	8.608%	$54.1194	$54.12	$54.10	$54.10
Purchase #6	$231.85	10.728%	$256.7229	$256.72	$256.70	$256.70
Purchase #7	$149.58	9.367%	$163.5912	$163.59	$163.60	$163.60
7 purchase totals =	$1,131.93		$1,215.5121	$1,215.51	$1,215.50	$1,215.50