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	$112.69	10.163%	$124.1427	$124.14	$124.15	$124.10
Purchase #2	$230.58	6.647%	$245.9067	$245.91	$245.90	$245.90
Purchase #3	$212.88	8.587%	$231.16	$231.16	$231.15	$231.20
Purchase #4	$53.76	4.337%	$56.0916	$56.09	$56.10	$56.10
Purchase #5	$84.93	5.338%	$89.4636	$89.46	$89.45	$89.50
Purchase #6	$203.42	6.209%	$216.0503	$216.05	$216.05	$216.10
Purchase #7	$99.69	12.611%	$112.2619	$112.26	$112.25	$112.30
7 purchase totals =	$997.95		$1,075.0768	$1,075.07	$1,075.05	$1,075.20