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	$129.91	9.517%	$142.2735	$142.27	$142.25	$142.30
Purchase #2	$151.88	5.741%	$160.5994	$160.60	$160.60	$160.60
Purchase #3	$37.62	5.333%	$39.6263	$39.63	$39.65	$39.60
Purchase #4	$78.64	4.678%	$82.3188	$82.32	$82.30	$82.30
Purchase #5	$63.72	6.843%	$68.0804	$68.08	$68.10	$68.10
Purchase #6	$67.43	9.466%	$73.8129	$73.81	$73.80	$73.80
Purchase #7	$78.68	10.429%	$86.8855	$86.89	$86.90	$86.90
7 purchase totals =	$607.88		$653.5968	$653.60	$653.60	$653.60