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	$53.37	4.342%	$55.6873	$55.69	$55.70	$55.70
Purchase #2	$27.26	3.730%	$28.2768	$28.28	$28.30	$28.30
Purchase #3	$235.62	13.488%	$267.4004	$267.40	$267.40	$267.40
Purchase #4	$188.39	4.283%	$196.4587	$196.46	$196.45	$196.50
Purchase #5	$164.37	7.463%	$176.6369	$176.64	$176.65	$176.60
Purchase #6	$144.85	11.667%	$161.7496	$161.75	$161.75	$161.70
Purchase #7	$100.65	10.574%	$111.2927	$111.29	$111.30	$111.30
7 purchase totals =	$914.51		$997.5024	$997.51	$997.55	$997.50