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	$159.46	11.674%	$178.0754	$178.08	$178.10	$178.10
Purchase #2	$48.28	13.347%	$54.7239	$54.72	$54.70	$54.70
Purchase #3	$20.90	11.556%	$23.3152	$23.32	$23.30	$23.30
Purchase #4	$40.86	13.743%	$46.4754	$46.48	$46.50	$46.50
Purchase #5	$66.27	4.208%	$69.0586	$69.06	$69.05	$69.10
Purchase #6	$79.59	7.312%	$85.4096	$85.41	$85.40	$85.40
Purchase #7	$30.81	5.119%	$32.3872	$32.39	$32.40	$32.40
7 purchase totals =	$446.17		$489.4453	$489.46	$489.45	$489.50