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	$114.96	13.361%	$130.3198	$130.32	$130.30	$130.30
Purchase #2	$198.81	12.119%	$222.9038	$222.90	$222.90	$222.90
Purchase #3	$155.91	3.683%	$161.6522	$161.65	$161.65	$161.70
Purchase #4	$136.77	8.640%	$148.5869	$148.59	$148.60	$148.60
Purchase #5	$46.90	3.233%	$48.4163	$48.42	$48.40	$48.40
Purchase #6	$103.98	9.141%	$113.4848	$113.48	$113.50	$113.50
Purchase #7	$154.64	13.685%	$175.8025	$175.80	$175.80	$175.80
7 purchase totals =	$911.97		$1,001.1663	$1,001.16	$1,001.15	$1,001.20