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	$102.96	12.758%	$116.0956	$116.10	$116.10	$116.10
Purchase #2	$233.39	5.161%	$245.4353	$245.44	$245.45	$245.40
Purchase #3	$97.35	5.400%	$102.6069	$102.61	$102.60	$102.60
Purchase #4	$158.30	9.843%	$173.8815	$173.88	$173.90	$173.90
Purchase #5	$236.90	12.505%	$266.5243	$266.52	$266.50	$266.50
Purchase #6	$91.75	9.656%	$100.6094	$100.61	$100.60	$100.60
Purchase #7	$101.28	3.490%	$104.8147	$104.81	$104.80	$104.80
7 purchase totals =	$1,021.93		$1,109.9677	$1,109.97	$1,109.95	$1,109.90