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	$64.50	5.398%	$67.9817	$67.98	$68.00	$68.00
Purchase #2	$180.33	5.670%	$190.5547	$190.55	$190.55	$190.60
Purchase #3	$51.99	13.668%	$59.096	$59.10	$59.10	$59.10
Purchase #4	$89.87	7.243%	$96.3793	$96.38	$96.40	$96.40
Purchase #5	$51.70	11.532%	$57.662	$57.66	$57.65	$57.70
Purchase #6	$142.90	7.158%	$153.1288	$153.13	$153.15	$153.10
Purchase #7	$224.46	8.826%	$244.2708	$244.27	$244.25	$244.30
7 purchase totals =	$805.75		$869.0733	$869.07	$869.10	$869.20