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	$192.35	9.446%	$210.5194	$210.52	$210.50	$210.50
Purchase #2	$78.90	5.511%	$83.2482	$83.25	$83.25	$83.20
Purchase #3	$48.57	4.524%	$50.7673	$50.77	$50.75	$50.80
Purchase #4	$64.65	10.762%	$71.6076	$71.61	$71.60	$71.60
Purchase #5	$153.36	8.311%	$166.1057	$166.11	$166.10	$166.10
Purchase #6	$215.27	12.390%	$241.942	$241.94	$241.95	$241.90
Purchase #7	$142.76	8.477%	$154.8618	$154.86	$154.85	$154.90
7 purchase totals =	$895.86		$979.0520	$979.06	$979.00	$979.00