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	$53.60	3.408%	$55.4267	$55.43	$55.45	$55.40
Purchase #2	$50.57	11.493%	$56.382	$56.38	$56.40	$56.40
Purchase #3	$89.27	4.349%	$93.1524	$93.15	$93.15	$93.20
Purchase #4	$187.61	4.829%	$196.6697	$196.67	$196.65	$196.70
Purchase #5	$36.51	6.434%	$38.8591	$38.86	$38.85	$38.90
Purchase #6	$180.31	6.785%	$192.544	$192.54	$192.55	$192.50
Purchase #7	$158.68	12.391%	$178.342	$178.34	$178.35	$178.30
7 purchase totals =	$756.55		$811.3759	$811.37	$811.40	$811.40