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	$54.52	10.195%	$60.0783	$60.08	$60.10	$60.10
Purchase #2	$82.48	3.394%	$85.2794	$85.28	$85.30	$85.30
Purchase #3	$99.94	3.117%	$103.0551	$103.06	$103.05	$103.10
Purchase #4	$231.94	13.214%	$262.5886	$262.59	$262.60	$262.60
Purchase #5	$224.89	3.719%	$233.2537	$233.25	$233.25	$233.30
Purchase #6	$79.47	4.403%	$82.9691	$82.97	$82.95	$83.00
Purchase #7	$195.56	11.726%	$218.4914	$218.49	$218.50	$218.50
7 purchase totals =	$968.80		$1,045.7156	$1,045.72	$1,045.75	$1,045.90