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	$51.59	5.850%	$54.608	$54.61	$54.60	$54.60
Purchase #2	$193.54	12.509%	$217.7499	$217.75	$217.75	$217.70
Purchase #3	$209.76	4.820%	$219.8704	$219.87	$219.85	$219.90
Purchase #4	$140.90	6.705%	$150.3473	$150.35	$150.35	$150.30
Purchase #5	$120.27	3.313%	$124.2545	$124.25	$124.25	$124.30
Purchase #6	$169.56	4.695%	$177.5208	$177.52	$177.50	$177.50
Purchase #7	$244.67	3.164%	$252.4114	$252.41	$252.40	$252.40
7 purchase totals =	$1,130.29		$1,196.7623	$1,196.76	$1,196.70	$1,196.70