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	$145.33	10.509%	$160.6027	$160.60	$160.60	$160.60
Purchase #2	$230.83	8.795%	$251.1315	$251.13	$251.15	$251.10
Purchase #3	$82.59	8.323%	$89.464	$89.46	$89.45	$89.50
Purchase #4	$59.93	9.444%	$65.5898	$65.59	$65.60	$65.60
Purchase #5	$219.58	5.125%	$230.8335	$230.83	$230.85	$230.80
Purchase #6	$165.37	9.310%	$180.7659	$180.77	$180.75	$180.80
Purchase #7	$47.84	12.250%	$53.7004	$53.70	$53.70	$53.70
7 purchase totals =	$951.47		$1,032.0878	$1,032.08	$1,032.10	$1,032.10