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	$151.59	9.182%	$165.509	$165.51	$165.50	$165.50
Purchase #2	$214.41	4.832%	$224.7703	$224.77	$224.75	$224.80
Purchase #3	$210.93	13.644%	$239.7093	$239.71	$239.70	$239.70
Purchase #4	$100.62	13.863%	$114.569	$114.57	$114.55	$114.60
Purchase #5	$200.61	5.814%	$212.2735	$212.27	$212.25	$212.30
Purchase #6	$164.30	12.547%	$184.9147	$184.91	$184.90	$184.90
Purchase #7	$37.33	3.236%	$38.538	$38.54	$38.55	$38.50
7 purchase totals =	$1,079.79		$1,180.2838	$1,180.28	$1,180.20	$1,180.30