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	$150.60	6.832%	$160.889	$160.89	$160.90	$160.90
Purchase #2	$55.62	12.554%	$62.6025	$62.60	$62.60	$62.60
Purchase #3	$181.46	5.347%	$191.1627	$191.16	$191.15	$191.20
Purchase #4	$241.64	8.454%	$262.0682	$262.07	$262.05	$262.10
Purchase #5	$75.56	3.523%	$78.222	$78.22	$78.20	$78.20
Purchase #6	$85.27	13.671%	$96.9273	$96.93	$96.95	$96.90
Purchase #7	$39.94	8.824%	$43.4643	$43.46	$43.45	$43.50
7 purchase totals =	$830.09		$895.3360	$895.33	$895.30	$895.40