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	$247.96	5.394%	$261.335	$261.34	$261.35	$261.30
Purchase #2	$85.91	4.134%	$89.4615	$89.46	$89.45	$89.50
Purchase #3	$193.96	12.327%	$217.8694	$217.87	$217.85	$217.90
Purchase #4	$208.64	10.667%	$230.8956	$230.90	$230.90	$230.90
Purchase #5	$158.64	12.556%	$178.5588	$178.56	$178.55	$178.60
Purchase #6	$145.88	3.544%	$151.05	$151.05	$151.05	$151.10
Purchase #7	$56.87	10.456%	$62.8163	$62.82	$62.80	$62.80
7 purchase totals =	$1,097.86		$1,191.9866	$1,192.00	$1,191.95	$1,192.10