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	$175.38	13.156%	$198.453	$198.45	$198.45	$198.50
Purchase #2	$40.42	5.651%	$42.7041	$42.70	$42.70	$42.70
Purchase #3	$25.97	11.381%	$28.9256	$28.93	$28.95	$28.90
Purchase #4	$224.98	8.519%	$244.146	$244.15	$244.15	$244.10
Purchase #5	$144.66	6.726%	$154.3898	$154.39	$154.40	$154.40
Purchase #6	$130.87	10.213%	$144.2358	$144.24	$144.25	$144.20
Purchase #7	$76.81	11.371%	$85.5441	$85.54	$85.55	$85.50
7 purchase totals =	$819.09		$898.3984	$898.40	$898.45	$898.30