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	$159.52	9.364%	$174.4575	$174.46	$174.45	$174.50
Purchase #2	$166.50	4.600%	$174.159	$174.16	$174.15	$174.20
Purchase #3	$144.73	6.867%	$154.6686	$154.67	$154.65	$154.70
Purchase #4	$49.77	11.482%	$55.4846	$55.48	$55.50	$55.50
Purchase #5	$92.89	10.734%	$102.8608	$102.86	$102.85	$102.90
Purchase #6	$146.55	8.109%	$158.4337	$158.43	$158.45	$158.40
Purchase #7	$149.75	3.503%	$154.9957	$155.00	$155.00	$155.00
7 purchase totals =	$909.71		$975.0599	$975.06	$975.05	$975.20