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	$177.46	5.532%	$187.2771	$187.28	$187.30	$187.30
Purchase #2	$53.36	11.586%	$59.5423	$59.54	$59.55	$59.50
Purchase #3	$153.40	13.213%	$173.6687	$173.67	$173.65	$173.70
Purchase #4	$143.54	10.455%	$158.5471	$158.55	$158.55	$158.50
Purchase #5	$105.57	6.641%	$112.5809	$112.58	$112.60	$112.60
Purchase #6	$100.43	11.415%	$111.8941	$111.89	$111.90	$111.90
Purchase #7	$46.42	5.418%	$48.935	$48.94	$48.95	$48.90
7 purchase totals =	$780.18		$852.4452	$852.45	$852.50	$852.40