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	$12.84	3.248%	$13.257	$13.26	$13.25	$13.30
Purchase #2	$13.64	3.605%	$14.1317	$14.13	$14.15	$14.10
Purchase #3	$146.91	7.704%	$158.2279	$158.23	$158.25	$158.20
Purchase #4	$74.82	9.293%	$81.773	$81.77	$81.75	$81.80
Purchase #5	$183.51	9.283%	$200.5452	$200.55	$200.55	$200.50
Purchase #6	$73.73	6.533%	$78.5468	$78.55	$78.55	$78.50
Purchase #7	$135.44	5.168%	$142.4395	$142.44	$142.45	$142.40
7 purchase totals =	$640.89		$688.9211	$688.93	$688.95	$688.80