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	$50.43	6.357%	$53.6358	$53.64	$53.65	$53.60
Purchase #2	$221.35	7.579%	$238.1261	$238.13	$238.15	$238.10
Purchase #3	$27.86	3.303%	$28.7802	$28.78	$28.80	$28.80
Purchase #4	$72.40	8.874%	$78.8248	$78.82	$78.80	$78.80
Purchase #5	$225.78	4.231%	$235.3328	$235.33	$235.35	$235.30
Purchase #6	$215.65	8.261%	$233.4648	$233.46	$233.45	$233.50
Purchase #7	$107.56	10.208%	$118.5397	$118.54	$118.55	$118.50
7 purchase totals =	$921.03		$986.7042	$986.70	$986.75	$986.60