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	$108.26	9.357%	$118.3899	$118.39	$118.40	$118.40
Purchase #2	$183.64	9.410%	$200.9205	$200.92	$200.90	$200.90
Purchase #3	$208.76	6.689%	$222.724	$222.72	$222.70	$222.70
Purchase #4	$207.83	6.758%	$221.8752	$221.88	$221.90	$221.90
Purchase #5	$94.51	4.370%	$98.6401	$98.64	$98.65	$98.60
Purchase #6	$174.94	5.801%	$185.0883	$185.09	$185.10	$185.10
Purchase #7	$50.81	6.598%	$54.1624	$54.16	$54.15	$54.20
7 purchase totals =	$1,028.75		$1,101.8004	$1,101.80	$1,101.80	$1,101.80