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	$223.85	6.632%	$238.6957	$238.70	$238.70	$238.70
Purchase #2	$70.51	13.704%	$80.1727	$80.17	$80.15	$80.20
Purchase #3	$185.64	5.322%	$195.5198	$195.52	$195.50	$195.50
Purchase #4	$221.47	3.523%	$229.2724	$229.27	$229.25	$229.30
Purchase #5	$71.64	9.444%	$78.4057	$78.41	$78.40	$78.40
Purchase #6	$207.45	5.435%	$218.7249	$218.72	$218.70	$218.70
Purchase #7	$227.76	10.495%	$251.6634	$251.66	$251.65	$251.70
7 purchase totals =	$1,208.32		$1,292.4546	$1,292.45	$1,292.35	$1,292.50