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	$235.87	12.830%	$266.1321	$266.13	$266.15	$266.10
Purchase #2	$80.52	3.159%	$83.0636	$83.06	$83.05	$83.10
Purchase #3	$12.51	4.163%	$13.0308	$13.03	$13.05	$13.00
Purchase #4	$149.85	3.150%	$154.5703	$154.57	$154.55	$154.60
Purchase #5	$84.33	9.594%	$92.4206	$92.42	$92.40	$92.40
Purchase #6	$178.61	5.219%	$187.9317	$187.93	$187.95	$187.90
Purchase #7	$194.51	12.535%	$218.8918	$218.89	$218.90	$218.90
7 purchase totals =	$936.20		$1,016.0409	$1,016.03	$1,016.05	$1,016.00