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	$104.54	9.309%	$114.2716	$114.27	$114.25	$114.30
Purchase #2	$145.82	9.429%	$159.5694	$159.57	$159.55	$159.60
Purchase #3	$140.59	13.160%	$159.0916	$159.09	$159.10	$159.10
Purchase #4	$189.76	11.562%	$211.7001	$211.70	$211.70	$211.70
Purchase #5	$78.74	11.795%	$88.0274	$88.03	$88.05	$88.00
Purchase #6	$191.82	12.540%	$215.8742	$215.87	$215.85	$215.90
Purchase #7	$48.59	9.246%	$53.0826	$53.08	$53.10	$53.10
7 purchase totals =	$899.86		$1,001.6169	$1,001.61	$1,001.60	$1,001.70