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	$158.47	13.741%	$180.2454	$180.25	$180.25	$180.20
Purchase #2	$39.95	9.241%	$43.6418	$43.64	$43.65	$43.60
Purchase #3	$85.80	3.625%	$88.9103	$88.91	$88.90	$88.90
Purchase #4	$133.38	10.471%	$147.3462	$147.35	$147.35	$147.30
Purchase #5	$244.40	4.109%	$254.4424	$254.44	$254.45	$254.40
Purchase #6	$232.29	13.873%	$264.5156	$264.52	$264.50	$264.50
Purchase #7	$176.39	7.509%	$189.6351	$189.64	$189.65	$189.60
7 purchase totals =	$1,070.68		$1,168.7368	$1,168.75	$1,168.75	$1,168.50