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	$13.87	5.792%	$14.6734	$14.67	$14.65	$14.70
Purchase #2	$142.80	8.373%	$154.7566	$154.76	$154.75	$154.80
Purchase #3	$139.55	11.176%	$155.1461	$155.15	$155.15	$155.10
Purchase #4	$195.50	10.383%	$215.7988	$215.80	$215.80	$215.80
Purchase #5	$166.79	9.154%	$182.058	$182.06	$182.05	$182.10
Purchase #6	$37.49	8.344%	$40.6182	$40.62	$40.60	$40.60
Purchase #7	$121.89	4.691%	$127.6079	$127.61	$127.60	$127.60
7 purchase totals =	$817.89		$890.6590	$890.67	$890.60	$890.70