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	$236.57	4.730%	$247.7598	$247.76	$247.75	$247.80
Purchase #2	$132.58	7.326%	$142.2928	$142.29	$142.30	$142.30
Purchase #3	$217.79	3.423%	$225.245	$225.25	$225.25	$225.20
Purchase #4	$71.46	9.359%	$78.1479	$78.15	$78.15	$78.10
Purchase #5	$49.77	13.322%	$56.4004	$56.40	$56.40	$56.40
Purchase #6	$93.38	9.271%	$102.0373	$102.04	$102.05	$102.00
Purchase #7	$98.52	13.422%	$111.7434	$111.74	$111.75	$111.70
7 purchase totals =	$900.07		$963.6266	$963.63	$963.65	$963.50