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	$204.30	6.396%	$217.367	$217.37	$217.35	$217.40
Purchase #2	$106.51	4.335%	$111.1272	$111.13	$111.15	$111.10
Purchase #3	$120.49	5.762%	$127.4326	$127.43	$127.45	$127.40
Purchase #4	$216.38	12.788%	$244.0507	$244.05	$244.05	$244.10
Purchase #5	$81.93	5.422%	$86.3722	$86.37	$86.35	$86.40
Purchase #6	$76.59	4.638%	$80.1422	$80.14	$80.15	$80.10
Purchase #7	$169.55	4.625%	$177.3917	$177.39	$177.40	$177.40
7 purchase totals =	$975.75		$1,043.8836	$1,043.88	$1,043.90	$1,043.90