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	$108.73	13.855%	$123.7945	$123.79	$123.80	$123.80
Purchase #2	$68.46	7.378%	$73.511	$73.51	$73.50	$73.50
Purchase #3	$99.56	11.467%	$110.9765	$110.98	$111.00	$111.00
Purchase #4	$200.92	6.755%	$214.4921	$214.49	$214.50	$214.50
Purchase #5	$225.95	3.477%	$233.8063	$233.81	$233.80	$233.80
Purchase #6	$212.30	4.826%	$222.5456	$222.55	$222.55	$222.50
Purchase #7	$194.64	7.103%	$208.4653	$208.47	$208.45	$208.50
7 purchase totals =	$1,110.56		$1,187.5913	$1,187.60	$1,187.60	$1,187.60