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	$151.84	3.711%	$157.4748	$157.47	$157.45	$157.50
Purchase #2	$163.46	10.403%	$180.4647	$180.46	$180.45	$180.50
Purchase #3	$139.39	4.729%	$145.9818	$145.98	$146.00	$146.00
Purchase #4	$68.98	12.301%	$77.4652	$77.47	$77.45	$77.50
Purchase #5	$199.85	11.519%	$222.8707	$222.87	$222.85	$222.90
Purchase #6	$222.88	3.254%	$230.1325	$230.13	$230.15	$230.10
Purchase #7	$178.26	10.430%	$196.8525	$196.85	$196.85	$196.90
7 purchase totals =	$1,124.66		$1,211.2422	$1,211.23	$1,211.20	$1,211.40