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	$117.56	11.510%	$131.0912	$131.09	$131.10	$131.10
Purchase #2	$191.79	12.373%	$215.5202	$215.52	$215.50	$215.50
Purchase #3	$230.50	11.717%	$257.5077	$257.51	$257.50	$257.50
Purchase #4	$158.91	3.598%	$164.6276	$164.63	$164.65	$164.60
Purchase #5	$50.95	5.135%	$53.5663	$53.57	$53.55	$53.60
Purchase #6	$167.30	3.514%	$173.1789	$173.18	$173.20	$173.20
Purchase #7	$139.69	6.363%	$148.5785	$148.58	$148.60	$148.60
7 purchase totals =	$1,056.70		$1,144.0704	$1,144.08	$1,144.10	$1,144.10