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	$239.67	6.525%	$255.3085	$255.31	$255.30	$255.30
Purchase #2	$89.72	12.152%	$100.6228	$100.62	$100.60	$100.60
Purchase #3	$114.39	6.546%	$121.878	$121.88	$121.90	$121.90
Purchase #4	$150.33	4.805%	$157.5534	$157.55	$157.55	$157.60
Purchase #5	$249.85	8.244%	$270.4476	$270.45	$270.45	$270.40
Purchase #6	$118.66	8.139%	$128.3177	$128.32	$128.30	$128.30
Purchase #7	$105.30	5.290%	$110.8704	$110.87	$110.85	$110.90
7 purchase totals =	$1,067.92		$1,144.9984	$1,145.00	$1,144.95	$1,145.00